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Fameli N, van Breemen C, Groschner K. Nanojunctions: Specificity of Ca 2+ signaling requires nano-scale architecture of intracellular membrane contact sites. Cell Calcium 2024; 117:102837. [PMID: 38011822 DOI: 10.1016/j.ceca.2023.102837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 10/31/2023] [Accepted: 11/17/2023] [Indexed: 11/29/2023]
Abstract
Spatio-temporal definition of Ca2+ signals involves the assembly of signaling complexes within the nano-architecture of contact sites between the sarco/endoplasmic reticulum (SR/ER) and the plasma membrane (PM). While the requirement of precise spatial assembly and positioning of the junctional signaling elements is well documented, the role of the nano-scale membrane architecture itself, as an ion-reflecting confinement of the signalling unit, remains as yet elusive. Utilizing the Na+/Ca2+ Exchanger-1 / SR/ER Ca2+ ATPase-2-mediated ER Ca2+ refilling process as a junctional signalling paradigm, we provide here the first evidence for an indispensable cellular function of the junctional membrane architecture. Our stochastic modeling approach demonstrates that junctional ER Ca2+ refilling operates exclusively at nano-scale membrane spacing, with a strong inverse relationship between junctional width and signaling efficiency. Our model predicts a breakdown of junctional Ca2+ signaling with loss of reflecting membrane confinement. In addition we consider interactions between Ca2+ and the phospholipid membrane surface, which may support interfacial Ca2+ transport and promote receptor targeting. Alterations in the molecular and nano-scale membrane organization at organelle-PM contacts are suggested as a new concept in pathophysiology.
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Affiliation(s)
| | - Cornelis van Breemen
- Department of Anesthesiology, Pharmacology, and Therapeutics, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Klaus Groschner
- Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical University of Graz, Graz, Austria.
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2
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Resveratrol Stimulates the Na+–Ca2+ Exchanger on the Plasma Membrane to Reduce Cytosolic Ca2+ in Rat Aortic Smooth Muscle Cells. J Cardiovasc Pharmacol 2020; 76:610-616. [DOI: 10.1097/fjc.0000000000000897] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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3
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Tran QK. Reciprocality Between Estrogen Biology and Calcium Signaling in the Cardiovascular System. Front Endocrinol (Lausanne) 2020; 11:568203. [PMID: 33133016 PMCID: PMC7550652 DOI: 10.3389/fendo.2020.568203] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 08/19/2020] [Indexed: 12/30/2022] Open
Abstract
17β-Estradiol (E2) is the main estrogenic hormone in the body and exerts many cardiovascular protective effects. Via three receptors known to date, including estrogen receptors α (ERα) and β (ERβ) and the G protein-coupled estrogen receptor 1 (GPER, aka GPR30), E2 regulates numerous calcium-dependent activities in cardiovascular tissues. Nevertheless, effects of E2 and its receptors on components of the calcium signaling machinery (CSM), the underlying mechanisms, and the linked functional impact are only beginning to be elucidated. A picture is emerging of the reciprocality between estrogen biology and Ca2+ signaling. Therein, E2 and GPER, via both E2-dependent and E2-independent actions, moderate Ca2+-dependent activities; in turn, ERα and GPER are regulated by Ca2+ at the receptor level and downstream signaling via a feedforward loop. This article reviews current understanding of the effects of E2 and its receptors on the cardiovascular CSM and vice versa with a focus on mechanisms and combined functional impact. An overview of the main CSM components in cardiovascular tissues will be first provided, followed by a brief review of estrogen receptors and their Ca2+-dependent regulation. The effects of estrogenic agonists to stimulate acute Ca2+ signals will then be reviewed. Subsequently, E2-dependent and E2-independent effects of GPER on components of the Ca2+ signals triggered by other stimuli will be discussed. Finally, a case study will illustrate how the many mechanisms are coordinated to moderate Ca2+-dependent activities in the cardiovascular system.
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Berra-Romani R, Guzmán-Silva A, Vargaz-Guadarrama A, Flores-Alonso JC, Alonso-Romero J, Treviño S, Sánchez-Gómez J, Coyotl-Santiago N, García-Carrasco M, Moccia F. Type 2 Diabetes Alters Intracellular Ca 2+ Handling in Native Endothelium of Excised Rat Aorta. Int J Mol Sci 2019; 21:ijms21010250. [PMID: 31905880 PMCID: PMC6982087 DOI: 10.3390/ijms21010250] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 12/24/2019] [Accepted: 12/25/2019] [Indexed: 02/03/2023] Open
Abstract
An increase in intracellular Ca2+ concentration ([Ca2+]i) plays a key role in controlling endothelial functions; however, it is still unclear whether endothelial Ca2+ handling is altered by type 2 diabetes mellitus, which results in severe endothelial dysfunction. Herein, we analyzed for the first time the Ca2+ response to the physiological autacoid ATP in native aortic endothelium of obese Zucker diabetic fatty (OZDF) rats and their lean controls, which are termed LZDF rats. By loading the endothelial monolayer with the Ca2+-sensitive fluorophore, Fura-2/AM, we found that the endothelial Ca2+ response to 20 µM and 300 µM ATP exhibited a higher plateau, a larger area under the curve and prolonged duration in OZDF rats. The “Ca2+ add-back” protocol revealed no difference in the inositol-1,4,5-trisphosphate-releasable endoplasmic reticulum (ER) Ca2+ pool, while store-operated Ca2+ entry was surprisingly down-regulated in OZDF aortae. Pharmacological manipulation disclosed that sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) activity was down-regulated by reactive oxygen species in native aortic endothelium of OZDF rats, thereby exaggerating the Ca2+ response to high agonist concentrations. These findings shed new light on the mechanisms by which type 2 diabetes mellitus may cause endothelial dysfunction by remodeling the intracellular Ca2+ toolkit.
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Affiliation(s)
- Roberto Berra-Romani
- Laboratory of Cardiovascular Physiology, Biomedicine School, Faculty of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico; (A.G.-S.); (J.A.-R.); (N.C.-S.)
- Correspondence: (R.B.-R.); (F.M.)
| | - Alejandro Guzmán-Silva
- Laboratory of Cardiovascular Physiology, Biomedicine School, Faculty of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico; (A.G.-S.); (J.A.-R.); (N.C.-S.)
| | - Ajelet Vargaz-Guadarrama
- Faculty of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico; (A.V.-G.); (J.S.-G.); (M.G.-C.)
| | - Juan Carlos Flores-Alonso
- Centro de Investigación Biomédica de Oriente, Instituto Mexicano del Seguro Social, Puebla 74360, Mexico;
| | - José Alonso-Romero
- Laboratory of Cardiovascular Physiology, Biomedicine School, Faculty of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico; (A.G.-S.); (J.A.-R.); (N.C.-S.)
| | - Samuel Treviño
- Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Puebla 72540, Mexico;
| | - Josué Sánchez-Gómez
- Faculty of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico; (A.V.-G.); (J.S.-G.); (M.G.-C.)
| | - Nayeli Coyotl-Santiago
- Laboratory of Cardiovascular Physiology, Biomedicine School, Faculty of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico; (A.G.-S.); (J.A.-R.); (N.C.-S.)
| | - Mario García-Carrasco
- Faculty of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico; (A.V.-G.); (J.S.-G.); (M.G.-C.)
| | - Francesco Moccia
- Laboratory of General Physiology, Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, 27100 Pavia, Italy
- Correspondence: (R.B.-R.); (F.M.)
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5
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IP 3 receptor signaling and endothelial barrier function. Cell Mol Life Sci 2017; 74:4189-4207. [PMID: 28803370 DOI: 10.1007/s00018-017-2624-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 07/18/2017] [Accepted: 08/08/2017] [Indexed: 12/14/2022]
Abstract
The endothelium, a monolayer of endothelial cells lining vessel walls, maintains tissue-fluid homeostasis by restricting the passage of the plasma proteins and blood cells into the interstitium. The ion Ca2+, a ubiquitous secondary messenger, initiates signal transduction events in endothelial cells that is critical to control of vascular tone and endothelial permeability. The ion Ca2+ is stored inside the intracellular organelles and released into the cytosol in response to environmental cues. The inositol 1,4,5-trisphosphate (IP3) messenger facilitates Ca2+ release through IP3 receptors which are Ca2+-selective intracellular channels located within the membrane of the endoplasmic reticulum. Binding of IP3 to the IP3Rs initiates assembly of IP3R clusters, a key event responsible for amplification of Ca2+ signals in endothelial cells. This review discusses emerging concepts related to architecture and dynamics of IP3R clusters, and their specific role in propagation of Ca2+ signals in endothelial cells.
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Di Giuro CML, Shrestha N, Malli R, Groschner K, van Breemen C, Fameli N. Na +/Ca 2+ exchangers and Orai channels jointly refill endoplasmic reticulum (ER) Ca 2+ via ER nanojunctions in vascular endothelial cells. Pflugers Arch 2017; 469:1287-1299. [PMID: 28497275 PMCID: PMC5590033 DOI: 10.1007/s00424-017-1989-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 04/20/2017] [Accepted: 04/24/2017] [Indexed: 11/29/2022]
Abstract
We investigated the role of Na+/ Ca2+ exchange (NCX) in the refilling of endoplasmic reticulum (ER) Ca2+ in vascular endothelial cells under various conditions of cell stimulation and plasma membrane (PM) polarization. Better understanding of the mechanisms behind basic ER Ca2+ content regulation is important, since current hypotheses on the possible ultimate causes of ER stress point to deterioration of the Ca2+ transport mechanism to/from ER itself. We measured [Ca2+]i temporal changes by Fura-2 fluorescence under experimental protocols that inhibit a host of transporters (NCX, Orai, non-selective transient receptor potential canonical (TRPC) channels, sarco/endoplasmic reticulum Ca2+ ATPase (SERCA), Na+/ K+ ATPase (NKA)) involved in the Ca2+ communication between the extracellular space and the ER. Following histamine-stimulated ER Ca2+ release, blockade of NCX Ca2+-influx mode (by 10 μM KB-R7943) diminished the ER refilling capacity by about 40%, while in Orai1 dominant negative-transfected cells NCX blockade attenuated ER refilling by about 60%. Conversely, inhibiting the ouabain sensitive NKA (10 nM ouabain), which may be localized in PM-ER junctions, increased the ER Ca2+ releasable fraction by about 20%, thereby supporting the hypothesis that this process of privileged ER refilling is junction-mediated. Junctions were observed in the cell ultrastructure and their main parameters of membrane separation and linear extension were (9.6 ± 3.8) nm and (128 ± 63) nm, respectively. Our findings point to a process of privileged refilling of the ER, in which NCX and store-operated Ca2+ entry via the stromal interaction molecule (STIM)-Orai system are the sole protagonists. These results shed light on the molecular machinery involved in the function of a previously hypothesized subplasmalemmal Ca2+ control unit during ER refilling with extracellular Ca2+.
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Affiliation(s)
| | - Niroj Shrestha
- Institute of Biophysics, Medical University of Graz, Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology & Biochemistry, Medical University of Graz, Graz, Austria
| | - Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Graz, Austria
| | - Cornelis van Breemen
- BC Children's Hospital Research Institute, Department of Anaesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nicola Fameli
- Institute of Biophysics, Medical University of Graz, Graz, Austria.
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Bondarenko AI, Montecucco F, Panasiuk O, Sagach V, Sidoryak N, Brandt KJ, Mach F. GPR55 agonist lysophosphatidylinositol and lysophosphatidylcholine inhibit endothelial cell hyperpolarization via GPR-independent suppression of Na +-Ca 2+ exchanger and endoplasmic reticulum Ca 2+ refilling. Vascul Pharmacol 2017; 89:39-48. [PMID: 28064014 DOI: 10.1016/j.vph.2017.01.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 12/21/2016] [Accepted: 01/03/2017] [Indexed: 11/18/2022]
Abstract
Lysophosphatidylinositol (LPI) and lysophosphatidylcholine (LPC) are lipid signaling molecules that induce endothelium-dependent vasodilation. In addition, LPC suppresses acetylcholine (Ach)-induced responses. We aimed to determine the influence of LPC and LPI on hyperpolarizing responses in vitro and in situ endothelial cells (EC) and identify the underlying mechanisms. Using patch-clamp method, we show that LPI and LPC inhibit EC hyperpolarization to histamine and suppress Na+/Ca2+ exchanged (NCX) currents in a concentration-dependent manner. The inhibition is non-mode-specific and unaffected by intracellular GDPβS infusion and tempol, a superoxide dismutase mimetic. In excised mouse aorta, LPI strongly inhibits the sustained and the peak endothelial hyperpolarization induced by Ach, but not by SKA-31, an opener of Ca2+-dependent K+ channels of intermediate and small conductance. The hyperpolarizing responses to consecutive histamine applications are strongly reduced by NCX inhibition. In a Ca2+-re-addition protocol, bepridil, a NCX inhibitor, and KB-R7943, a blocker of reversed NCX, inhibit the hyperpolarizing responses to Ca2+-re-addition following Ca2+ stores depletion. These finding indicate that LPC and LPI inhibit endothelial hyperpolarization to Ach and histamine independently of G-protein coupled receptors and superoxide anions. Reversed NCX is critical for ER Ca2+ refilling in EC. The inhibition of NCX by LPI and LPC underlies diminished endothelium-dependent responses and endothelial dysfunction accompanied by increased levels of these lipids in the blood.
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Affiliation(s)
- Alexander I Bondarenko
- Circulatory Physiology Department, Bogomoletz Institute of Physiology NAS of Ukraine, Bogomoletz Str.4, 01024 Kiev, Ukraine; Medical University of Graz, Institute of Molecular Biology and Biochemistry, Graz 8010, Austria.
| | - Fabrizio Montecucco
- First Clinic of Internal Medicine, Department of Internal Medicine, University of Genoa, 6 viale Benedetto XV, 16132 Genoa, Italy; IRCCS AOU San Martino - IST Istituto Nazionale per la Ricerca sul Cancro, Largo Benzi 10, 16132 Genoa, Italy
| | - Olga Panasiuk
- Circulatory Physiology Department, Bogomoletz Institute of Physiology NAS of Ukraine, Bogomoletz Str.4, 01024 Kiev, Ukraine
| | - Vadim Sagach
- Circulatory Physiology Department, Bogomoletz Institute of Physiology NAS of Ukraine, Bogomoletz Str.4, 01024 Kiev, Ukraine
| | - Nataliya Sidoryak
- Department of Physiology of Human and Animals, Melitopol State Pedagogical University, Ukraine
| | - Karim J Brandt
- Division of Cardiology, Foundation for Medical Researches, Department of Internal Medicine, University of Geneva, Av. de la Roseraie 64, CH-1211 Geneva 4, Switzerland
| | - François Mach
- Division of Cardiology, Foundation for Medical Researches, Department of Internal Medicine, University of Geneva, Av. de la Roseraie 64, CH-1211 Geneva 4, Switzerland
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Tran QK, Firkins R, Giles J, Francis S, Matnishian V, Tran P, VerMeer M, Jasurda J, Burgard MA, Gebert-Oberle B. Estrogen Enhances Linkage in the Vascular Endothelial Calmodulin Network via a Feedforward Mechanism at the G Protein-coupled Estrogen Receptor 1. J Biol Chem 2016; 291:10805-23. [PMID: 26987903 DOI: 10.1074/jbc.m115.697334] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Indexed: 12/13/2022] Open
Abstract
Estrogen exerts many effects on the vascular endothelium. Calmodulin (CaM) is the transducer of Ca(2+) signals and is a limiting factor in cardiovascular tissues. It is unknown whether and how estrogen modifies endothelial functions via the network of CaM-dependent proteins. Here we show that 17β-estradiol (E2) up-regulates total CaM level in endothelial cells. Concurrent measurement of Ca(2+) and Ca(2+)-CaM indicated that E2 also increases free Ca(2+)-CaM. Pharmacological studies, gene silencing, and receptor expression-specific cell studies indicated that the G protein-coupled estrogen receptor 1 (GPER/GPR30) mediates these effects via transactivation of EGFR and subsequent MAPK activation. The outcomes were then examined on four distinct members of the intracellular CaM target network, including GPER/GPR30 itself and estrogen receptor α, the plasma membrane Ca(2+)-ATPase (PMCA), and endothelial nitric-oxide synthase (eNOS). E2 substantially increases CaM binding to estrogen receptor α and GPER/GPR30. Mutations that reduced CaM binding to GPER/GPR30 in separate binding domains do not affect GPER/GPR30-Gβγ preassociation but decrease GPER/GPR30-mediated ERK1/2 phosphorylation. E2 increases CaM-PMCA association, but the expected stimulation of Ca(2+) efflux is reversed by E2-stimulated tyrosine phosphorylation of PMCA. These effects sustain Ca(2+) signals and promote Ca(2+)-dependent CaM interactions with other CaM targets. Consequently, E2 doubles CaM-eNOS interaction and also promotes dual phosphorylation of eNOS at Ser-617 and Ser-1179. Calculations using in-cell and in vitro data revealed substantial individual and combined contribution of these effects to total eNOS activity. Taken together, E2 generates a feedforward loop via GPER/GPR30, which enhances Ca(2+)/CaM signals and functional linkage in the endothelial CaM target network.
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Affiliation(s)
- Quang-Kim Tran
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Rachel Firkins
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Jennifer Giles
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Sarah Francis
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Vahe Matnishian
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Phuong Tran
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Mark VerMeer
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Jake Jasurda
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Michelle Ann Burgard
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Briana Gebert-Oberle
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
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Functional impairment of endothelial cells by the antimycotic amphotericin B. Biochem Biophys Res Commun 2016; 472:40-5. [PMID: 26902113 DOI: 10.1016/j.bbrc.2016.02.054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 02/15/2016] [Indexed: 11/21/2022]
Abstract
We set out to determine the membrane potential (Vm) of the endothelial cell line EA.hy926 and its sensitivity to the antimycotic amphotericin B (AmB), a commonly used antifungal component in cell culture media. We measured the endothelial Vm under various experimental conditions by patch clamp technique and found that Vm of AmB-treated cells is (-12.1 ± 9.3) mV, while in AmB-untreated (control) cells it is (-57.1 ± 4.1) mV. In AmB-free extracellular solutions, Vm recovered toward control levels and this gain in Vm rapidly dissipated upon re-addition of AmB, demonstrating a rapid and reversible effect of AmB on endothelial Vm. The consequences of AmB dependent alterations in endothelial transmembrane potential were tested at the levels of Ca(2+) signaling, of nucleotide concentrations, and energy metabolism. In AmB-treated cells we found substantially reduced Ca(2+) entry (to about 60% of that in control cells) in response to histamine induced endoplasmic reticulum (ER) Ca(2+) depletion, and diminished the ATP-to-ADP ratio (by >30%). Our data demonstrate a marked and experimentally relevant dependence of basic functional parameters of cultured endothelial cells on the presence of the ionophoric antimycotic AmB. The profound and reversible effects of the widely used culture media component AmB need careful consideration when interpreting experimental data obtained under respective culture conditions.
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Tran QK, VerMeer M, Burgard MA, Hassan AB, Giles J. Hetero-oligomeric Complex between the G Protein-coupled Estrogen Receptor 1 and the Plasma Membrane Ca2+-ATPase 4b. J Biol Chem 2015; 290:13293-307. [PMID: 25847233 DOI: 10.1074/jbc.m114.628743] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Indexed: 11/06/2022] Open
Abstract
The new G protein-coupled estrogen receptor 1 (GPER/GPR30) plays important roles in many organ systems. The plasma membrane Ca(2+)-ATPase (PMCA) is essential for removal of cytoplasmic Ca(2+) and for shaping the time courses of Ca(2+)-dependent activities. Here, we show that PMCA and GPER/GPR30 physically interact and functionally influence each other. In primary endothelial cells, GPER/GPR30 agonist G-1 decreases PMCA-mediated Ca(2+) extrusion by promoting PMCA tyrosine phosphorylation. GPER/GPR30 overexpression decreases PMCA activity, and G-1 further potentiates this effect. GPER/GPR30 knockdown increases PMCA activity, whereas PMCA knockdown substantially reduces GPER/GPR30-mediated phosphorylation of the extracellular signal-related kinase (ERK1/2). GPER/GPR30 co-immunoprecipitates with PMCA with or without treatment with 17β-estradiol, thapsigargin, or G-1. Heterologously expressed GPER/GPR30 in HEK 293 cells co-localizes with PMCA4b, the main endothelial PMCA isoform. Endothelial cells robustly express the PDZ post-synaptic density protein (PSD)-95, whose knockdown reduces the association between GPER/GPR30 and PMCA. Additionally, the association between PMCA4b and GPER/GPR30 is substantially reduced by truncation of either or both of their C-terminal PDZ-binding motifs. Functionally, inhibition of PMCA activity is significantly reduced by truncation of GPER/GPR30's C-terminal PDZ-binding motif. These data strongly indicate that GPER/GPR30 and PMCA4b form a hetero-oligomeric complex in part via the anchoring action of PSD-95, in which they constitutively affect each other's function. Activation of GPER/GPR30 further inhibits PMCA activity through tyrosine phosphorylation of the pump. These interactions represent cross-talk between Ca(2+) signaling and GPER/GPR30-mediated activities.
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Affiliation(s)
- Quang-Kim Tran
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Mark VerMeer
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Michelle A Burgard
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Ali B Hassan
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Jennifer Giles
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
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Ewart MA, Kennedy S, Macmillan D, Raja ALN, Watt IM, Currie S. Altered vascular smooth muscle function in the ApoE knockout mouse during the progression of atherosclerosis. Atherosclerosis 2014; 234:154-61. [PMID: 24657385 PMCID: PMC3997800 DOI: 10.1016/j.atherosclerosis.2014.02.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 01/29/2014] [Accepted: 02/18/2014] [Indexed: 02/07/2023]
Abstract
Objectives Relaxation of vascular smooth muscle (VSM) requires re-uptake of cytosolic Ca2+ into the sarcoplasmic reticulum (SR) via the Sarco/Endoplasmic Reticulum Ca2+ ATPase (SERCA), or extrusion via the Plasma Membrane Ca2+ ATPase (PMCA) or sodium Ca2+ exchanger (NCX). Peroxynitrite, a reactive species formed in vascular inflammatory diseases, upregulates SERCA activity to induce relaxation but, chronically, can contribute to atherogenesis and altered vascular function by escalating endoplasmic reticulum stress. Our objectives were to determine if peroxynitrite-induced relaxation and Ca2+ handling processes within vascular smooth muscle cells were altered as atherosclerosis develops. Methods Aortae from control and ApoE−/− mice were studied histologically, functionally and for protein expression levels of SERCA and PMCA. Ca2+ responses were assessed in dissociated aortic smooth muscle cells in the presence and absence of extracellular Ca2+. Results Relaxation to peroxynitrite was concentration-dependent and endothelium-independent. The abilities of the SERCA blocker thapsigargin and the PMCA inhibitor carboxyeosin to block this relaxation were altered during fat feeding and plaque progression. SERCA levels were progressively reduced, while PMCA expression was upregulated. In ApoE−/− VSM cells, increases in cytosolic Ca2+ [Ca2+]c in response to SERCA blockade were reduced, while SERCA-independent Ca2+ clearance was faster compared to control. Conclusion As atherosclerosis develops in the ApoE−/− mouse, expression and function of Ca2+ handling proteins are altered. Up-regulation of Ca2+ removal via PMCA may offer a potential compensatory mechanism to help normalise the dysfunctional relaxation observed during disease progression. Expression and function of SERCA and PMCA are temporally altered in ApoE−/− VSM. TG-induced increases in [Ca2+]c were reduced in ApoE−/− aortic SM cells. Ca2+ extrusion is upregulated in isolated ApoE−/− aortic SM cells.
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Affiliation(s)
- Marie-Ann Ewart
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, G12 8QQ, UK.
| | - Simon Kennedy
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, G12 8QQ, UK
| | - Debbi Macmillan
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow G4 0NR, UK
| | - Abhirami L N Raja
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, G12 8QQ, UK
| | - Ian M Watt
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, G12 8QQ, UK
| | - Susan Currie
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow G4 0NR, UK
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12
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Grossini E, Molinari C, Sigaudo L, Biella M, Mary DASG, Vacca G. Calcium handling in porcine coronary endothelial cells by gastrin-17. J Mol Endocrinol 2013; 50:243-53. [PMID: 23349211 DOI: 10.1530/jme-12-0148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In porcine coronary artery endothelial cells (PCAEC), gastrin-17 has recently been found to increase nitric oxide (NO) production by the endothelial NO synthase (eNOS) isoform through cholecystokinin 1/2 (CCK1/2) receptors and the involvement of protein kinase A (PKA), PKC and the β2-adrenoreceptor-related pathway. As eNOS is the Ca(2)(+)-dependent isoform of the enzyme, we aimed to examine the effects of gastrin-17 on Ca(2)(+) movements. Thus, experiments were performed in Fura-2-acetoxymethyl-ester-loaded PCAEC, where changes of cytosolic Ca(2)(+) ([Ca(2)(+)]c) caused by gastrin-17 were analysed and compared with those of CCK receptors and β2-adrenoreceptors agonists/antagonists. In addition, some experiments were performed by stimulating cells with gastrin-17 in the presence or absence of cAMP/PKA activator/inhibitor and of phospholipase C (PLC) and Ca(2)(+)-calmodulin dependent protein kinase II (CaMKII) blockers. The results have shown that gastrin-17 can promote a transient increase in [Ca(2)(+)]c mainly originating from an intracellular pool sensitive to thapsigargin and from the extracellular space. In addition, the response of cells to gastrin-17 was increased by the adenylyl cyclase activator and the β2-adrenoreceptor agonists and affected mainly by the CCK2 receptor agonists/antagonists. Moreover, the effects of gastrin-17 were prevented by β2-adrenoreceptors and CaMKII blockers and the adenylyl cyclase/PKA and PLC inhibitors. Finally, in PCAEC cultured in Na(+)-free medium or loaded with the plasma membrane Ca(2)(+) pump inhibitor, the gastrin-17-evoked Ca(2)(+) transient was long lasting. In conclusion, this study shows that gastrin-17 affected intracellular Ca(2)(+) homeostasis in PCAEC by both promoting a discharge of an intracellular pool and by interfering with the operation of store-dependent channels through mainly CCK2 receptors and PKA/PLC- and CaMKII-related signalling downstream of β2-adrenoreceptor stimulation.
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Affiliation(s)
- E Grossini
- Department of Translational Medicine, Biotechnology Centre for Applicated Medical Research (BRMA), University of East Piedmont A. Avogadro, Novara, Italy.
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Moccia F, Berra-Romani R, Tanzi F. Update on vascular endothelial Ca 2+ signalling: A tale of ion channels, pumps and transporters. World J Biol Chem 2012; 3:127-58. [PMID: 22905291 PMCID: PMC3421132 DOI: 10.4331/wjbc.v3.i7.127] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/04/2012] [Accepted: 07/11/2012] [Indexed: 02/05/2023] Open
Abstract
A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and forms a multifunctional transducing organ that mediates a plethora of cardiovascular processes. The activation of ECs from as state of quiescence is, therefore, regarded among the early events leading to the onset and progression of potentially lethal diseases, such as hypertension, myocardial infarction, brain stroke, and tumor. Intracellular Ca2+ signals have long been know to play a central role in the complex network of signaling pathways regulating the endothelial functions. Notably, recent work has outlined how any change in the pattern of expression of endothelial channels, transporters and pumps involved in the modulation of intracellular Ca2+ levels may dramatically affect whole body homeostasis. Vascular ECs may react to both mechanical and chemical stimuli by generating a variety of intracellular Ca2+ signals, ranging from brief, localized Ca2+ pulses to prolonged Ca2+ oscillations engulfing the whole cytoplasm. The well-defined spatiotemporal profile of the subcellular Ca2+ signals elicited in ECs by specific extracellular inputs depends on the interaction between Ca2+ releasing channels, which are located both on the plasma membrane and in a number of intracellular organelles, and Ca2+ removing systems. The present article aims to summarize both the past and recent literature in the field to provide a clear-cut picture of our current knowledge on the molecular nature and the role played by the components of the Ca2+ machinery in vascular ECs under both physiological and pathological conditions.
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Affiliation(s)
- Francesco Moccia
- Francesco Moccia, Franco Tanzi, Department of Biology and Biotechnologies "Lazzaro Spallanzani", Laboratory of Physiology, University of Pavia, Via Forlanini 6, 27100 Pavia, Italy
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Shen B, Kwan HY, Ma X, Wong CO, Du J, Huang Y, Yao X. cAMP activates TRPC6 channels via the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB)-mitogen-activated protein kinase kinase (MEK)-ERK1/2 signaling pathway. J Biol Chem 2011; 286:19439-45. [PMID: 21487005 DOI: 10.1074/jbc.m110.210294] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
cAMP is an important second messenger that executes diverse physiological function in living cells. In this study, we investigated the effect of cAMP on canonical TRPC6 (transient receptor potential channel 6) channels in TRPC6-expressing HEK293 cells and glomerular mesangial cells. The results showed that 500 μm 8-Br-cAMP, a cell-permeable analog of cAMP, elicited [Ca(2+)](i) increases and stimulated a cation current at the whole-cell level in TRPC6-expressing HEK293 cells. The effect of cAMP diminished in the presence of the PI3K inhibitors wortmannin and LY294002 or the MEK inhibitors PD98059, U0126, and MEK inhibitor I. 8-Br-cAMP also induced phosphorylation of MEK and ERK1/2. Conversion of serine to glycine at an ERK1/2 phosphorylation site (S281G) abolished the cAMP activation of TRPC6 as determined by whole-cell and cell-attached single-channel patch recordings. Experiments based on a panel of pharmacological inhibitors or activators suggested that the cAMP action on TRPC6 was not mediated by PKA, PKG, or EPAC (exchange protein activated by cAMP). Total internal fluorescence reflection microscopy showed that 8-Br-cAMP did not alter the trafficking of TRPC6 to the plasma membrane. We also found that, in glomerular mesangial cells, glucagon-induced [Ca(2+)](i) increases were mediated through the cAMP-PI3K-PKB-MEK-ERK1/2-TRPC6 signaling pathway. In summary, this study uncovered a novel TRPC6 activation mechanism in which cAMP activates TRPC6 via the PI3K-PKB-MEK-ERK1/2 signaling pathway.
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Affiliation(s)
- Bing Shen
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
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Zhou M, Widmer RJ, Xie W, Jimmy Widmer A, Miller MW, Schroeder F, Parker JL, Heaps CL. Effects of exercise training on cellular mechanisms of endothelial nitric oxide synthase regulation in coronary arteries after chronic occlusion. Am J Physiol Heart Circ Physiol 2010; 298:H1857-69. [PMID: 20363881 DOI: 10.1152/ajpheart.00754.2009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Exercise training enhances agonist-mediated relaxation in both control and collateral-dependent coronary arteries of hearts subjected to chronic occlusion, an enhancement that is mediated in part by nitric oxide. The purpose of the present study was to elucidate exercise training-induced adaptations in specific cellular mechanisms involved in the regulation of endothelial nitric oxide synthase (eNOS) in coronary arteries of ischemic hearts. Ameroid constrictors were surgically placed around the proximal left circumflex coronary artery (LCX) of adult female Yucatan miniature swine. Eight weeks postoperatively, animals were randomized into sedentary (pen-confined) or exercise training (treadmill run; 5 days/wk; 14 wk) protocols. Coronary artery segments ( approximately 1.0 mm luminal diameter) were isolated from collateral-dependent (LCX) and control (nonoccluded left anterior descending) arteries 22 wk after ameroid placement. Endothelial cells were enzymatically dissociated, and intracellular Ca(2+) responses (fura 2) to bradykinin stimulation were studied. Immunofluorescence and laser scanning confocal microscopy were used to quantify endothelial cell eNOS and caveolin-1 cellular distribution under basal and bradykinin-stimulated conditions. Immunoblot analysis was used to determine eNOS, phosphorylated (p)-eNOS, protein kinase B (Akt), pAkt, and caveolin-1 protein levels. Bradykinin-stimulated nitrite plus nitrate (NOx; nitric oxide metabolites) levels were assessed via HPLC. Exercise training resulted in significantly enhanced bradykinin-mediated increases in endothelial Ca(2+) levels, NOx levels, and the distribution of eNOS-to-caveolin-1 ratio at the plasma membrane in endothelial cells of control and collateral-dependent arteries. Exercise training also significantly increased total eNOS and phosphorylated levels of eNOS (pSer(1179)) in collateral-dependent arteries. Total eNOS protein levels were also significantly increased in collateral-dependent arteries of sedentary animals. These data provide new insights into exercise training-induced adaptations in cellular mechanisms of nitric oxide regulation in collateral-dependent coronary arteries of chronically occluded hearts that contribute to enhanced nitric oxide production.
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Affiliation(s)
- Minglong Zhou
- Department of Veterinary Physiology and Pharmacology, Texas A&M Univ., College Station, TX 77843, USA
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16
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Na+-Ca2+ exchanger contributes to Ca2+ extrusion in ATP-stimulated endothelium of intact rat aorta. Biochem Biophys Res Commun 2010; 395:126-30. [PMID: 20353753 DOI: 10.1016/j.bbrc.2010.03.153] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 03/25/2010] [Indexed: 11/20/2022]
Abstract
The role of Na(+)-Ca(2+) exchanger (NCX) in vascular endothelium is still matter of debate. Depending on both the endothelial cell (EC) type and the extracellular ligand, NCX has been shown to operate in either the forward (Ca(2+) out)- or the reverse (Ca(2+) in)-mode. In particular, acetylcholine (Ach) has been shown to promote Ca(2+) inflow in the intact endothelium of excised rat aorta. Herein, we assessed the involvement of NCX into the Ca(2+) signals elicited by ATP in such preparation. Removal of extracellular Na(+) (0Na(+)) causes the NCX to switch into the reverse-mode and induced an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), which disappeared in the absence of extracellular Ca(2+), and in the presence of benzamil, which blocks both modes of NCX, and KB-R 7943, a selective inhibitor of the reverse-mode. ATP induced a transient Ca(2+) signal, whose decay was significantly prolonged by 0Na(+), benzamil, DCB, and monensin while it was unaffected by KB-R 7943. Notably, lowering extracellular Na(+) concentration increased the sensibility to lower doses of ATP. These date suggest that, unlike Ach-stimulated ECs, NCX promotes Ca(2+) extrusion when the stimulus is provided by ATP in intact endothelium of rat aorta. These data show that, within the same preparation, NCX operates in both modes, depending on the chemical nature of the extracellular stimulus.
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17
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Endothelial nitric oxide attenuates Na+/Ca2+ exchanger-mediated vasoconstriction in rat aorta. Br J Pharmacol 2008; 154:982-90. [PMID: 18469841 DOI: 10.1038/bjp.2008.178] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE The Na+/Ca2+ exchanger (NCX) may be an important modulator of Ca2+ entry and exit. The present study investigated whether NCX was affected by prostacyclin and nitric oxide (NO) released from the vascular endothelium, as NCX contains phosphorylation sites for PKA and PKG. EXPERIMENTAL APPROACH Rat aortic rings were set up in organ baths. Tension was measured across the ring with a force transducer. KEY RESULTS Lowering extracellular [Na+] ([Na+]o) to 1.18 mM induced vasoconstriction in rat endothelium-denuded aortic rings. This effect was blocked by the NCX inhibitor KB-R7943 (2-2-[4-(4-nitrobenzyloxy)phenyl] ethyl isothiourea methanesulphonate; 1 microM). In endothelium-intact aortic rings, decreasing [Na+]o did not constrict the aortic rings significantly, but after treatment with the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one; 1 microM) or the NOS inhibitor L-NAME (N(omega)-nitro-L-arginine methyl ester; 50 microM), a vasoconstriction that was similar in size to that in endothelium-denuded preparations was evident. The vasorelaxation induced by the NO donor sodium nitroprusside sodium nitroprusside dihydrate (30 nM) was the same in the endothelium-denuded aortic rings preconstricted with either low Na+ (1.18 mM), the thromboxane A2 agonist U46619 (9,11-dideoxy-9alpha, 11alpha-methanoepoxy prostaglandin F(2alpha); 0.1 microM) or high K+ (80 mM). CONCLUSIONS AND IMPLICATIONS The results suggest that the endothelium inhibits NCX operation via guanylate cyclase/NO. This is stronger than for other constrictors such as phenylephrine and may relate to concomitant NCX-stimulated NO release from the endothelium. This finding may be important where NCX operates in reverse mode, such as during ischaemia, and highlights a new mechanism whereby the endothelium modulates Ca2+ homoeostasis in vascular smooth muscle.
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Liang W, McDonald P, McManus B, van Breemen C, Wang X. P2Y2 Receptor-Mediated Ca2+ Signaling and Spontaneous Ca2+ Releases in Human Valvular Myofibroblasts. Int Heart J 2008; 49:221-36. [DOI: 10.1536/ihj.49.221] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Willmann Liang
- School of Biological Sciences, Nanyang Technological University
| | - Paul McDonald
- The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, University of British Columbia
| | - Bruce McManus
- The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, University of British Columbia
| | - Cornelis van Breemen
- The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, University of British Columbia
| | - Xiaodong Wang
- The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, University of British Columbia
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Abstract
Caveolae are associated with molecules crucial for calcium handling. This review considers the roles of caveolae in calcium handling for smooth muscle and interstitial cells of Cajal (ICC). Structural studies showed that the plasma membrane calcium pump (PMCA), a sodium-calcium exchanger (NCX1), and a myogenic nNOS appear to be colocalized with caveolin I, the main constituent of these caveolae. Voltage dependent calcium channels (VDCC) are associated but not co-localized with caveolin 1, as are proteins of the peripheral sarcoplasmic reticulum (SR) such as calreticulin. Only the nNOS is absent from caveolin 1 knockout animals. Functional studies in calcium free media sugest that a source of calcium in tonic smooth muscles exists, partly sequestered from extracellular EGTA. This source supported sustained contractions to carbachol using VDCC and dependent on activity of the SERCA pump. This source is postulated to be caveolae, near peripheral SR. New evidence, presented here, suggests that a similar source exists in phasic smooth muscle of the intestine and its ICC. These results suggest that caveolae and peripheral SR are a functional unit recycling calcium through VDCC and controlling its local concentration. Calcium handling molecules associated with caveolae in smooth muscle and ICC were identified and their possible functions also reviewed.
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Affiliation(s)
- E E Daniel
- Department Of Pharmacology, University of Alberta, Edmonton, Canada.
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20
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Pittner J, Rhinehart K, Pallone TL. Ouabain modulation of endothelial calcium signaling in descending vasa recta. Am J Physiol Renal Physiol 2006; 291:F761-9. [PMID: 16597612 DOI: 10.1152/ajprenal.00326.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Using fura 2-loaded vessels, we tested whether ouabain modulates endothelial cytoplasmic calcium concentration ([Ca(2+)](CYT)) in rat descending vasa recta (DVR). Over a broad range between 10(-10) and 10(-4) M, ouabain elicited biphasic peak and plateau [Ca(2+)](CYT) elevations. Blockade of voltage-gated Ca(2+) entry with nifedipine did not affect the response to ouabain mitigating against a role for myo-endothelial gap junctions. Reduction of extracellular Na(+) concentration ([Na(+)](o)) or Na(+)/Ca(2+) exchanger (NCX) inhibition with SEA-0400 (10(-6) M) elevated [Ca(2+)](CYT), supporting a role for NCX in the setting of basal [Ca(2+)](CYT). SEA-0400 abolished the [Ca(2+)](CYT) response to ouabain implicating NCX as a mediator. The transient peak phase of [Ca(2+)](CYT) elevation that followed either ouabain or reduction of [Na(+)](o) was abolished by 2-aminoethoxydiphenyl borate (5 x 10(-5) M). Cation channel blockade with La(3+) (10 muM) or SKF-96365 (10 muM) also attenuated the ouabain-induced [Ca(2+)](CYT) response. Ouabain pretreatment increased the [Ca(2+)](CYT) elevation elicited by bradykinin (10(-7) M). We conclude that inhibition of ouabain-sensitive Na(+)-K(+)-ATPase enhances DVR endothelial Ca(2+) store loading and modulates [Ca(2+)](CYT) signaling through mechanisms that involve NCX, Ca(2+) release, and cation channel activation.
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Affiliation(s)
- János Pittner
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Pande J, Grover AK. Plasma membrane calcium pumps in smooth muscle: from fictional molecules to novel inhibitors. Can J Physiol Pharmacol 2005; 83:743-54. [PMID: 16333376 DOI: 10.1139/y05-075] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Plasma membrane Ca2+pumps (PMCA pumps) are Ca2+-Mg2+ATPases that expel Ca2+from the cytosol to extracellular space and are pivotal to cell survival and function. PMCA pumps are encoded by the genes PMCA1, -2, -3, and -4. Alternative splicing results in a large number of isoforms that differ in their kinetics and activation by calmodulin and protein kinases A and C. Expression by 4 genes and a multifactorial regulation provide redundancy to allow for animal survival despite genetic defects. Heterozygous mice with ablation of any of the PMCA genes survive and only the homozygous mice with PMCA1 ablation are embryolethal. Some PMCA isoforms may also be involved in other cell functions. Biochemical and biophysical studies of PMCA pumps have been limited by their low levels of expression. Delineation of the exact physiological roles of PMCA pumps has been difficult since most cells also express sarco/endoplasmic reticulum Ca2+pumps and a Na+-Ca2+-exchanger, both of which can lower cytosolic Ca2+. A major limitation in the field has been the lack of specific inhibitors of PMCA pumps. More recently, a class of inhibitors named caloxins have emerged, and these may aid in delineating the roles of PMCA pumps.Key words: ATPases, hypertension, caloxin, protein kinase A, protein kinase C, calmodulin.
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Affiliation(s)
- Jyoti Pande
- Department of Medicine, McMaster University, Hamilton, ON, Canada
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22
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Liang W, Buluc M, van Breemen C, Wang X. Vectorial Ca2+ release via ryanodine receptors contributes to Ca2+ extrusion from freshly isolated rabbit aortic endothelial cells. Cell Calcium 2005; 36:431-43. [PMID: 15451626 DOI: 10.1016/j.ceca.2004.04.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Revised: 04/06/2004] [Accepted: 04/07/2004] [Indexed: 11/19/2022]
Abstract
In this study, we identified ryanodine receptors (RyRs) as a component of a cytosolic Ca(2+) removal pathway in freshly isolated rabbit aortic endothelial cells. In an earlier article, we reported that the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) and Na(+)/Ca(2+) exchanger (NCX) function in series to extrude cytosolic Ca(2+) to the extracellular space. Here we employed caffeine and ryanodine as modulators of RyR and showed that they act as the linkage between SERCA and NCX in removing Ca(2+) from the cytoplasm. Our data indicate that both 15 mM caffeine and 1 microM ryanodine facilitated Ca(2+) extrusion by activating RyRs while 100 microM ryanodine had the opposite effect by blocking RyRs. A further attempt to investigate RyR pharmacology revealed that in the absence of extracellular Ca(2+), ryanodine at 1 microM, but not 100 microM, stimulated Ca(2+) loss from the endoplasmic reticulum (ER). Blockade of RyR had no effect on the Ca(2+) removal rate when NCX had been previously blocked. In addition, the localization of RyR was determined using confocal microscopy of BODIPY TR-X fluorescent staining. Taken together, our findings suggest that in freshly isolated endothelial cells Ca(2+) is removed in part by transport through SERCA, RyR, and eventually NCX, and that RyR and NCX are in close functional proximity near the plasma membrane. After blockade of this component, Ca(2+) extrusion could be further inhibited by carboxyeosin, indicating a parallel contribution by the plasmalemmal Ca(2+)-ATPase (PMCA).
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Affiliation(s)
- Willmann Liang
- Department of Pharmacology and Therapeutics, The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, St. Paul's Hospital, University of British Columbia, Vancouver, BC V6Z 1Y6, Canada
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Taubert D, Rosenkranz A, Berkels R, Roesen R, Schömig E. Acute effects of glucose and insulin on vascular endothelium. Diabetologia 2004; 47:2059-71. [PMID: 15662548 DOI: 10.1007/s00125-004-1586-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2004] [Accepted: 07/22/2004] [Indexed: 10/26/2022]
Abstract
AIMS/HYPOTHESIS Chronic exposure to high concentrations of glucose has consistently been demonstrated to impair endothelium-dependent, nitric oxide (NO)-mediated vasodilation. In contrast, several clinical investigations have reported that acute exposure to high glucose, alone or in combination with insulin, triggers vasodilation. The aim of this study was to examine whether elevated glucose itself stimulates endothelial NO formation or enhances insulin-mediated endothelial NO release. METHODS We measured NO release and vessel tone ex vivo in porcine coronary conduit arteries (PCAs). Intracellular Ca(2+) was monitored in porcine aortic endothelial cells (PAECs) by fura-2 fluorescence. Expression of the Na(+)/glucose cotransporter-1 (SGLT-1) was assayed in PAECs and PCA endothelium by RT-PCR. RESULTS Stimulation of PCAs with D: -glucose, but not the osmotic control L: -glucose, induced a transient increase in NO release (EC(50) approximately 10 mmol/l), mediated by a rise in intracellular Ca(2+) levels due to an influx from the extracellular space. This effect was abolished by inhibitors of the plasmalemmal Na(+)/Ca(2+) exchanger (dichlorobenzamil) and the SGLT-1 (phlorizin), which was found to be expressed in aortic and coronary endothelium. Alone, D: -glucose did not relax PCA, but did augment the effect of insulin on NO release and vasodilation. CONCLUSIONS/INTERPRETATION An increased supply of extracellular D: -glucose appears to enhance the activity of the endothelial isoform of nitric oxide synthase by increasing intracellular Na(+) concentrations via SGLT-1, which in turn stimulates an extracellular Ca(2+) influx through the Na(+)/Ca(2+) exchanger. This mechanism may be responsible for glucose-enhanced, insulin-dependent increases in tissue perfusion (including coronary blood-flow), thus accelerating glucose extraction from the blood circulation to limit the adverse vascular effects of prolonged hyperglycaemia.
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Affiliation(s)
- D Taubert
- Department of Pharmacology, Medical Hospital of the University of Cologne, Gleueler Str. 24, 50931, Cologne, Germany.
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Brown RC, Mark KS, Egleton RD, Davis TP. Protection against hypoxia-induced blood-brain barrier disruption: changes in intracellular calcium. Am J Physiol Cell Physiol 2004; 286:C1045-52. [PMID: 15075203 DOI: 10.1152/ajpcell.00360.2003] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tissue damage after stroke is partly due to disruption of the blood-brain barrier (BBB). Little is known about the role of calcium in modulating BBB disruption. We investigated the effect of hypoxic and aglycemic stress on BBB function and intracellular calcium levels. Bovine brain microvessel endothelial cells were treated with A-23187 to increase intracellular calcium without hypoxia or treated with a calcium chelator (BAPTA) or calcium channel blockers (nifedipine or SKF-96365) and 6 h of hypoxia. A-23187 alone did not increase paracellular permeability. Hypoxia increased intracellular calcium, and hypoxia or hypoxia-aglycemia increased paracellular permeability. Treatment with nifedipine and SKF-96365 increased intracellular calcium under normoglycemic conditions, instead of blocking calcium influx, and was protective against hypoxia-induced BBB disruption under normoglycemia. Protection by nifedipine and SKF-96365 was not due to antioxidant properties of these compounds. These data indicate that increased intracellular calcium alone is not enough to disrupt the BBB. However, increased intracellular calcium after drug treatment and hypoxia suggests a potential mechanism for these drugs in BBB protection; nifedipine and SKF-96365 plus hypoxic stress may trigger calcium-mediated signaling cascades, altering BBB integrity.
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Affiliation(s)
- Rachel C Brown
- Dept. of Pharmacology, PO Box 24-5050, The Univ. of Arizona College of Medicine, 1501 N. Campbell Ave., Tucson, AZ 85724-5050, USA
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Chan C, Harland ML, Webb SE, Chen J, Miller AL, Barritt GJ. Evaluation, using targeted aequorins, of the roles of the endoplasmic reticulum and its (Ca2++Mg2+)ATP-ases in the activation of store-operated Ca2+ channels in liver cells. Cell Calcium 2004; 35:317-31. [PMID: 15036949 DOI: 10.1016/j.ceca.2003.09.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2002] [Revised: 08/11/2003] [Accepted: 09/05/2003] [Indexed: 11/20/2022]
Abstract
The process by which store-operated Ca2+ channels (SOCs) deliver Ca2+ to the endoplasmic reticulum (ER) and the role of (Ca2++Mg2+)ATP-ases of the ER in the activation of SOCs in H4-IIE liver cells were investigated using cell lines stably transfected with apo-aequorin targeted to the cytoplasmic space or the ER. In order to measure the concentration of Ca2+ in the ER ([Ca2+]er), cells were pre-treated with 2,5-di-tert-butylhydroquinone (DBHQ) to deplete Ca2+ in the ER before reconstitution of holo-aequorin. The addition of extracellular Ca2+ (Cao2+) to Ca2+-depleted cells induced refilling of the ER, which was complete within 5 min. This was associated with a sharp transient increase in the cytoplasmic Ca2+ concentration ([Ca2+]cyt) of about 15 s duration (a Cao2+-induced [Ca2+]cyt spike) after which [Ca2+]cyt remained elevated slightly above the basal value for a period of about 2 min (low [Ca2+]cyt plateau). The Cao2+-induced [Ca2+]cyt spike was inhibited by Gd3+, not affected by tetrakis-(2-pyridymethyl) ethylenediamine (TPEN), and broadened by ionomycin and the intracellular Ca2+ chelators BAPTA and EGTA. Refilling of the ER was inhibited by caffeine. Neither thapsigargin nor DBHQ caused a detectable inhibition or change in shape of the Cao2+-induced [Ca2+]cyt spike or the low [Ca2+]cyt plateau whereas each inhibited the inflow of Ca2+ to the ER by about 80%. Experiments conducted with carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) indicated that thapsigargin did not alter the amount of Ca2+ accumulated in mitochondria. The changes in [Ca2+]cyt reported by aequorin were compared with those reported by fura-2. It is concluded that (i) there are significant quantitative differences between the manner in which aequorin and fura-2 sense changes in [Ca2+]cyt and (ii) thapsigargin and DBHQ inhibit the uptake of Ca2+ to the bulk of the ER but this is not associated with inhibition of the activation of SOCs. The possible involvement of a small sub-region of the ER (or another intracellular Ca2+ store), which contains thapsigargin-insensitive (Ca2++Mg2+)ATP-ases, in the activation of SOCs is briefly discussed.
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Affiliation(s)
- Caroline Chan
- Department of Biology, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Lau KL, Kong SK, Ko WH, Kwan HY, Huang Y, Yao X. cGMP stimulates endoplasmic reticulum Ca(2+)-ATPase in vascular endothelial cells. Life Sci 2003; 73:2019-28. [PMID: 12899926 DOI: 10.1016/s0024-3205(03)00565-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Calcium is a crucial regulator of many physiological processes such as cell growth, division, differentiation, cell death and apoptosis. In this study, we examined the effect of cGMP on agonist-induced [Ca(2+)](i) transient in isolated rat aortic endothelial cells. 100 microM ATP was applied to the cells bathed in a Ca(2+)-free physiological solution to induce a [Ca(2+)](i) transient that was caused by Ca(2+) release from intracellular stores. cGMP, which was applied after [Ca(2+)](i) reached its peak level, accelerated the falling phase of [Ca(2+)](i) transient. Pre-treatment of the cells with CPA abolished the accelerating effect of cGMP on the falling phase of [Ca(2+)](i) transient. The effect of cGMP was reversed by KT5823, a highly specific inhibitor of protein kinase G. Taken together, these data suggest that cGMP may reduce [Ca(2+)](i) level by promoting Ca(2+) uptake through sarcoplasmic/endoplasmic reticulum ATPase and that the effect of cGMP may be mediated by protein kinase G.
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Affiliation(s)
- Kin-Ling Lau
- Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, N.T., Hong Kong
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Abstract
Measurements of cellular Ca2+-calmodulin concentrations have suggested that competition for limiting calmodulin may couple calmodulin-dependent activities. Here we have directly tested this hypothesis. We have found that in endothelial cells the amount of calmodulin bound to nitric-oxide synthase and the catalytic activity of the enzyme both are increased approximately 3-fold upon changes in the phosphorylation status of the enzyme. Quantitative immunoblotting indicates that the synthase can bind up to 25% of the total cellular calmodulin. Consistent with this, simultaneous determinations of the free Ca2+ and Ca2+-calmodulin concentrations in these cells performed using indo-1 and a fluorescent calmodulin biosensor (Kd = 2 nm) indicate that increased binding of calmodulin to the synthase is associated with substantial reductions in the Ca2+-calmodulin concentrations produced and an increase in the [Ca2+]50 for formation of the calmodulin-biosensor complex. The physiological significance of these effects is confirmed by a corresponding 40% reduction in calmodulin-dependent plasma membrane Ca2+ pump activity. An identical reduction in pump activity is produced by expression of a high affinity (Kd = 0.3 nm) calmodulin biosensor, and treatment to increase calmodulin binding to the synthase then has no further effect. This suggests that the observed reduction in pump activity is due specifically to reduced calmodulin availability. Increases in synthase activity thus appear to be coupled to decreases in the activities of other calmodulin targets through reductions in the size of a limiting pool of available calmodulin. This exemplifies what is likely to be a ubiquitous mechanism for coupling among diverse calmodulin-dependent activities.
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Affiliation(s)
- Quang-Kim Tran
- Division of Molecular Biology & Biochemistry, School of Biological Sciences, University of Missouri, Kansas City 64110-2499, USA
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Abstract
Nitric oxide production is stimulated by an increase of the concentration of cytosolic Ca(2+) in vascular endothelial cells. Recent evidence suggests that nitric oxide and cGMP might attenuate Ca(2+) influx and, at the same time, initiate a Ca(2+) removal mechanism, thereby decreasing the intracellular concentration of endothelial Ca(2+) in a negative feedback fashion. Such a negative feedback mechanism could serve to protect the endothelial cells from the detrimental effects of excessive nitric oxide and Ca(2+).
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Affiliation(s)
- Xiaoqiang Yao
- Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.
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