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Prüschenk S, Majer M, Schlossmann J. Novel Functional Features of cGMP Substrate Proteins IRAG1 and IRAG2. Int J Mol Sci 2023; 24:9837. [PMID: 37372987 DOI: 10.3390/ijms24129837] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/01/2023] [Accepted: 06/05/2023] [Indexed: 06/29/2023] Open
Abstract
The inositol triphosphate-associated proteins IRAG1 and IRAG2 are cGMP kinase substrate proteins that regulate intracellular Ca2+. Previously, IRAG1 was discovered as a 125 kDa membrane protein at the endoplasmic reticulum, which is associated with the intracellular Ca2+ channel IP3R-I and the PKGIβ and inhibits IP3R-I upon PKGIβ-mediated phosphorylation. IRAG2 is a 75 kDa membrane protein homolog of IRAG1 and was recently also determined as a PKGI substrate. Several (patho-)physiological functions of IRAG1 and IRAG2 were meanwhile elucidated in a variety of human and murine tissues, e.g., of IRAG1 in various smooth muscles, heart, platelets, and other blood cells, of IRAG2 in the pancreas, heart, platelets, and taste cells. Hence, lack of IRAG1 or IRAG2 leads to diverse phenotypes in these organs, e.g., smooth muscle and platelet disorders or secretory deficiency, respectively. This review aims to highlight the recent research regarding these two regulatory proteins to envision their molecular and (patho-)physiological tasks and to unravel their functional interplay as possible (patho-)physiological counterparts.
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Affiliation(s)
- Sally Prüschenk
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Regensburg, 93040 Regensburg, Germany
| | - Michael Majer
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Regensburg, 93040 Regensburg, Germany
| | - Jens Schlossmann
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Regensburg, 93040 Regensburg, Germany
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Okumura W, Kozono T, Sato H, Matsui H, Takagi T, Tonozuka T, Nishikawa A. Jaw1/LRMP increases Ca 2+ influx upon GPCR stimulation with heterogeneous effect on the activity of each ITPR subtype. Sci Rep 2022; 12:9476. [PMID: 35676525 PMCID: PMC9177832 DOI: 10.1038/s41598-022-13620-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 05/11/2022] [Indexed: 11/24/2022] Open
Abstract
Ca2+ influx upon G protein-coupled receptor (GPCR) stimulation is observed as a cytosolic Ca2+ concentration oscillation crucial to initiating downstream responses including cell proliferation, differentiation, and cell–cell communication. Although Jaw1 is known to interact with inositol 1,4,5-triphosphate receptor (ITPRs), Ca2+ channels on the endoplasmic reticulum, the function of Jaw1 in the Ca2+ dynamics with physiological stimulation remains unclear. In this study, using inducible Jaw1-expressing HEK293 cells, we showed that Jaw1 increases Ca2+ influx by GPCR stimulation via changing the Ca2+ influx oscillation pattern. Furthermore, we showed that Jaw1 increases the Ca2+ release activity of all ITPR subtypes in a subtly different manner. It is well known that the Ca2+ influx oscillation pattern varies from cell type to cell type, therefore these findings provide an insight into the relationship between the heterogeneous Ca2+ dynamics and the specific ITPR and Jaw1 expression patterns.
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Affiliation(s)
- Wataru Okumura
- Department of Food and Energy Systems Science, Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan
| | - Takuma Kozono
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan
| | - Hiroyuki Sato
- Cooperative Major in Advanced Health Science, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan
| | - Hitomi Matsui
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan
| | - Tsubasa Takagi
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan
| | - Takashi Tonozuka
- Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan
| | - Atsushi Nishikawa
- Department of Food and Energy Systems Science, Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan. .,Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan. .,Cooperative Major in Advanced Health Science, Tokyo University of Agriculture and Technology, Tokyo, 184-8588, Japan. .,Department of Applied Biological Chemistry, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8509, Japan.
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Arige V, Terry LE, Malik S, Knebel TR, Wagner II LE, Yule DI. CREB regulates the expression of type 1 inositol 1,4,5-trisphosphate receptors. J Cell Sci 2021; 134:jcs258875. [PMID: 34533188 PMCID: PMC8601716 DOI: 10.1242/jcs.258875] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 09/13/2021] [Indexed: 12/16/2022] Open
Abstract
Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) play a central role in regulating intracellular Ca2+ signals in response to a variety of internal and external cues. Dysregulation of IP3R signaling is the underlying cause for numerous pathological conditions. It is well established that the activities of IP3Rs are governed by several post-translational modifications, including phosphorylation by protein kinase A (PKA). However, the long-term effects of PKA activation on expression of IP3R subtypes remains largely unexplored. In this report, we investigate the effects of chronic stimulation and tonic activity of PKA on the expression of IP3R subtypes. We demonstrate that expression of the type 1 IP3R (IP3R1) is augmented upon prolonged activation of PKA or upon ectopic overexpression of cyclic AMP-response element-binding protein (CREB) without altering IP3R2 and IP3R3 abundance. By contrast, inhibition of PKA or blocking CREB diminished IP3R1 expression. We also demonstrate that agonist-induced Ca2+-release mediated by IP3R1 is significantly attenuated upon blocking of CREB. Moreover, CREB - by regulating the expression of KRAS-induced actin-interacting protein (KRAP) - ensures correct localization and licensing of IP3R1. Overall, we report a crucial role for CREB in governing both the expression and correct localization of IP3R1. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
| | | | | | | | | | - David I. Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
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Activation of cyclic GMP-dependent protein kinase blocks alcohol-mediated cell death and calcium disruption in cerebellar granule neurons. Neurosci Lett 2018; 676:108-112. [PMID: 29679679 DOI: 10.1016/j.neulet.2018.04.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 04/09/2018] [Accepted: 04/16/2018] [Indexed: 01/10/2023]
Abstract
Alcohol during brain development leads to the widespread neuronal death observed in fetal alcohol spectrum disorders (FASD). In comparison, the mature brain is less vulnerable to alcohol. Studies into maturation-acquired alcohol resistance uncovered a protective mechanism that reduces alcohol-induced neuronal death through nitric oxide-cGMP-cyclic GMP-dependent protein kinase (NO-cGMP-cGK) signaling. However, the downstream processes underlying this neuroprotection remain unclear. Alcohol can disrupt levels of intracellular calcium ([Ca2+]i) in vulnerable neuronal populations to trigger cell death in both in vivo and in vitro models of FASD. Since cGK has been demonstrated to regulate and inhibit intracellular Ca2+ release, we examined the hypothesis that cGK confers alcohol resistance by preventing [Ca2+]i disruptions. Alcohol resistance, determined by neuronal survival after 24 h of alcohol exposure, was examined in primary cerebellar granule neuron (CGN) cultures derived from 5 to 7 day-old neonatal mice with an activator, 8-Br-cGMP, and/or an inhibitor, Rp-8-pCPT-cGMPS, of cGK signaling. Intracellular Ca2+ responses to alcohol were measured by ratiometric Ca2+ imaging in Fura-2-loaded CGN cultures after 8-Br-cGMP treatment. Our results indicate that activating cGK with 8-Br-cGMP before alcohol administration provided neuroprotection, which the cGK inhibitor, Rp-8-pCPT-cGMPS, blocked. Alcohol exposure elevated [Ca2+]i, whereas 8-Br-cGMP pretreatment reduced both the level of the alcohol-induced rise in [Ca2+]i as well as the number of cells that responded to alcohol by increasing [Ca2+]i. These findings associate alcohol resistance, mediated by cGK signaling, to reduction of the persistent and toxic increase in [Ca2+]i from alcohol exposure.
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Baker SA, Drumm BT, Cobine CA, Keef KD, Sanders KM. Inhibitory Neural Regulation of the Ca 2+ Transients in Intramuscular Interstitial Cells of Cajal in the Small Intestine. Front Physiol 2018; 9:328. [PMID: 29686622 PMCID: PMC5900014 DOI: 10.3389/fphys.2018.00328] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/15/2018] [Indexed: 01/03/2023] Open
Abstract
Gastrointestinal motility is coordinated by enteric neurons. Both inhibitory and excitatory motor neurons innervate the syncytium consisting of smooth muscle cells (SMCs) interstitial cells of Cajal (ICC) and PDGFRα+ cells (SIP syncytium). Confocal imaging of mouse small intestines from animals expressing GCaMP3 in ICC were used to investigate inhibitory neural regulation of ICC in the deep muscular plexus (ICC-DMP). We hypothesized that Ca2+ signaling in ICC-DMP can be modulated by inhibitory enteric neural input. ICC-DMP lie in close proximity to the varicosities of motor neurons and generate ongoing Ca2+ transients that underlie activation of Ca2+-dependent Cl- channels and regulate the excitability of SMCs in the SIP syncytium. Electrical field stimulation (EFS) caused inhibition of Ca2+ for the first 2-3 s of stimulation, and then Ca2+ transients escaped from inhibition. The NO donor (DEA-NONOate) inhibited Ca2+ transients and Nω-Nitro-L-arginine (L-NNA) or a guanylate cyclase inhibitor (ODQ) blocked inhibition induced by EFS. Purinergic neurotransmission did not affect Ca2+ transients in ICC-DMP. Purinergic neurotransmission elicits hyperpolarization of the SIP syncytium by activation of K+ channels in PDGFRα+ cells. Generalized hyperpolarization of SIP cells by pinacidil (KATP agonist) or MRS2365 (P2Y1 agonist) also had no effect on Ca2+ transients in ICC-DMP. Peptidergic transmitter receptors (VIP and PACAP) are expressed in ICC and can modulate ICC-DMP Ca2+ transients. In summary Ca2+ transients in ICC-DMP are blocked by enteric inhibitory neurotransmission. ICC-DMP lack a voltage-dependent mechanism for regulating Ca2+ release, and this protects Ca2+ handling in ICC-DMP from membrane potential changes in other SIP cells.
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Affiliation(s)
| | | | | | | | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada, Reno, NV, United States
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Cyclic AMP Recruits a Discrete Intracellular Ca 2+ Store by Unmasking Hypersensitive IP 3 Receptors. Cell Rep 2017; 18:711-722. [PMID: 28099849 PMCID: PMC5276804 DOI: 10.1016/j.celrep.2016.12.058] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 11/17/2016] [Accepted: 12/19/2016] [Indexed: 12/12/2022] Open
Abstract
Inositol 1,4,5-trisphosphate (IP3) stimulates Ca2+ release from the endoplasmic reticulum (ER), and the response is potentiated by 3′,5′-cyclic AMP (cAMP). We investigated this interaction in HEK293 cells using carbachol and parathyroid hormone (PTH) to stimulate formation of IP3 and cAMP, respectively. PTH alone had no effect on the cytosolic Ca2+ concentration, but it potentiated the Ca2+ signals evoked by carbachol. Surprisingly, however, the intracellular Ca2+ stores that respond to carbachol alone could be both emptied and refilled without affecting the subsequent response to PTH. We provide evidence that PTH unmasks high-affinity IP3 receptors within a discrete Ca2+ store. We conclude that Ca2+ stores within the ER that dynamically exchange Ca2+ with the cytosol maintain a functional independence that allows one store to be released by carbachol and another to be released by carbachol with PTH. Compartmentalization of ER Ca2+ stores adds versatility to IP3-evoked Ca2+ signals. Cyclic AMP directly potentiates IP3-evoked Ca2+ release The Ca2+ stores released by IP3 alone or IP3 with cAMP are functionally independent Cyclic AMP unmasks high-affinity IP3 receptors in a discrete ER Ca2+ store Independent regulation of discrete Ca2+ stores increases signaling versatility
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Taylor EJA, Pantazaka E, Shelley KL, Taylor CW. Prostaglandin E 2 Inhibits Histamine-Evoked Ca 2+ Release in Human Aortic Smooth Muscle Cells through Hyperactive cAMP Signaling Junctions and Protein Kinase A. Mol Pharmacol 2017; 92:533-545. [PMID: 28877931 PMCID: PMC5635517 DOI: 10.1124/mol.117.109249] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 08/23/2017] [Indexed: 11/22/2022] Open
Abstract
In human aortic smooth muscle cells, prostaglandin E2 (PGE2) stimulates adenylyl cyclase (AC) and attenuates the increase in intracellular free Ca2+ concentration evoked by activation of histamine H1 receptors. The mechanisms are not resolved. We show that cAMP mediates inhibition of histamine-evoked Ca2+ signals by PGE2. Exchange proteins activated by cAMP were not required, but the effects were attenuated by inhibition of cAMP-dependent protein kinase (PKA). PGE2 had no effect on the Ca2+ signals evoked by protease-activated receptors, heterologously expressed muscarinic M3 receptors, or by direct activation of inositol 1,4,5-trisphosphate (IP3) receptors by photolysis of caged IP3. The rate of Ca2+ removal from the cytosol was unaffected by PGE2, but PGE2 attenuated histamine-evoked IP3 accumulation. Substantial inhibition of AC had no effect on the concentration-dependent inhibition of Ca2+ signals by PGE2 or butaprost (to activate EP2 receptors selectively), but it modestly attenuated responses to EP4 receptors, activation of which generated less cAMP than EP2 receptors. We conclude that inhibition of histamine-evoked Ca2+ signals by PGE2 occurs through “hyperactive signaling junctions,” wherein cAMP is locally delivered to PKA at supersaturating concentrations to cause uncoupling of H1 receptors from phospholipase C. This sequence allows digital signaling from PGE2 receptors, through cAMP and PKA, to histamine-evoked Ca2+ signals.
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Affiliation(s)
- Emily J A Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Evangelia Pantazaka
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Kathryn L Shelley
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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Taylor CW. Regulation of IP 3 receptors by cyclic AMP. Cell Calcium 2016; 63:48-52. [PMID: 27836216 PMCID: PMC5471599 DOI: 10.1016/j.ceca.2016.10.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 10/27/2016] [Accepted: 10/27/2016] [Indexed: 01/01/2023]
Abstract
Ca2+ and cAMP are ubiquitous intracellular messengers and interactions between them are commonplace. Here the effects of cAMP on inositol 1,4,5-trisphosphate receptors (IP3Rs) are briefly reviewed. All three subtypes of IP3R are phosphorylated by cAMP-dependent protein kinase (PKA). This potentiates IP3-evoked Ca2+ release through IP3R1 and IP3R2, but probably has little effect on IP3R3. In addition, cAMP can directly sensitize all three IP3R subtypes to IP3. The high concentrations of cAMP required for this PKA-independent modulation of IP3Rs is delivered to them within signalling junctions that include type 6 adenylyl cyclase and IP3R2.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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Chandrasekhar R, Alzayady KJ, Wagner LE, Yule DI. Unique Regulatory Properties of Heterotetrameric Inositol 1,4,5-Trisphosphate Receptors Revealed by Studying Concatenated Receptor Constructs. J Biol Chem 2016; 291:4846-60. [PMID: 26755721 DOI: 10.1074/jbc.m115.705301] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Indexed: 02/02/2023] Open
Abstract
The ability of inositol 1,4,5-trisphosphate receptors (IP3R) to precisely initiate and generate a diverse variety of intracellular Ca(2+) signals is in part mediated by the differential regulation of the three subtypes (R1, R2, and R3) by key functional modulators (IP3, Ca(2+), and ATP). However, the contribution of IP3R heterotetramerization to Ca(2+) signal diversity has largely been unexplored. In this report, we provide the first definitive biochemical evidence of endogenous heterotetramer formation. Additionally, we examine the contribution of individual subtypes within defined concatenated heterotetramers to the shaping of Ca(2+) signals. Under conditions where key regulators of IP3R function are optimal for Ca(2+) release, we demonstrate that individual monomers within heteromeric IP3Rs contributed equally toward generating a distinct 'blended' sensitivity to IP3 that is likely dictated by the unique IP3 binding affinity of the heteromers. However, under suboptimal conditions where [ATP] were varied, we found that one subtype dictated the ATP regulatory properties of heteromers. We show that R2 monomers within a heterotetramer were both necessary and sufficient to dictate the ATP regulatory properties. Finally, the ATP-binding site B in R2 critical for ATP regulation was mutated and rendered non-functional to address questions relating to the stoichiometry of IP3R regulation. Two intact R2 monomers were sufficient to maintain ATP regulation in R2 homotetramers. In summary, we demonstrate that heterotetrameric IP3R do not necessarily behave as the sum of the constituent subunits, and these properties likely extend the versatility of IP3-induced Ca(2+) signaling in cells expressing multiple IP3R isoforms.
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Affiliation(s)
- Rahul Chandrasekhar
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Kamil J Alzayady
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Larry E Wagner
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - David I Yule
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
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Shih CY, Lin IH, Ding JC, Chen FC, Chou TC. Antiplatelet activity of nifedipine is mediated by inhibition of NF-κB activation caused by enhancement of PPAR-β/-γ activity. Br J Pharmacol 2014; 171:1490-1500. [PMID: 24730061 DOI: 10.1111/bph.12523] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND AND PURPOSE The transcription factor NF-κB, stimulates platelet aggregation through a non-genomic mechanism. Nifedipine, a voltage-gated L-type calcium channel blocker, is widely used to treat hypertension. Nifedipine also displays antiplatelet activity, but the underlying mechanisms involved remain unclear. This study was designed to investigate whether the antiplatelet effects of nifedipine are mediated by regulating NF-κB-dependent responses. EXPERIMENTAL APPROACH Platelet aggregation was measured turbidimetrically using an aggregometer. NF-κB and PPAR activation, intracellular Ca2+ mobilization, PKCα activity, surface glycoprotein IIb/IIIa (GPIIb/IIIa) expression and platelet activation-related signalling pathways were determined in control and nifedipine-treated platelets in the presence or absence of PPAR antagonists or betulinic acid, a NF-κB activator. KEY RESULTS Exposure of platelets to nifedipine significantly increased the PPAR-β/-γ activity in activated human platelets. Treatment with nifedipine reduced collagen-induced NF-κB events, including the phosphorylation of IκB kinase-β, IκBα and p65NF-κB, which were markedly attenuated by GSK0660, a PPAR-β antagonist, or GW9662, a PPAR-γ antagonist. Furthermore, the interaction of PPAR-β/-γ with NF-κB and the PPAR-β/-γ-up-regulated NO/cGMP/PKG1 cascade may contribute to inhibition of NF-κB activation by nifedipine. Suppressing PPAR-β/-γ activity or increasing NF-κB activation greatly reversed the inhibitory effect of nifedipine on collagen-induced platelet aggregation, intracellular Ca2+ mobilization, PKCα activity and surface GPIIb/IIIa expression.CONCLUSIONS AND IMPLICATIONSPPAR-β/-γ-dependent inhibition of NF-κB activation contributes to the antiplatelet activity of nifedipine. These findings provide a novel mechanism underlying the beneficial effects of nifedipine on platelet hyperactivity-related vascular and inflammatory diseases.
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Alzayady KJ, Wagner LE, Chandrasekhar R, Monteagudo A, Godiska R, Tall GG, Joseph SK, Yule DI. Functional inositol 1,4,5-trisphosphate receptors assembled from concatenated homo- and heteromeric subunits. J Biol Chem 2013; 288:29772-84. [PMID: 23955339 DOI: 10.1074/jbc.m113.502203] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Vertebrate genomes code for three subtypes of inositol 1,4,5-trisphosphate (IP3) receptors (IP3R1, -2, and -3). Individual IP3R monomers are assembled to form homo- and heterotetrameric channels that mediate Ca(2+) release from intracellular stores. IP3R subtypes are regulated differentially by IP3, Ca(2+), ATP, and various other cellular factors and events. IP3R subtypes are seldom expressed in isolation in individual cell types, and cells often express different complements of IP3R subtypes. When multiple subtypes of IP3R are co-expressed, the subunit composition of channels cannot be specifically defined. Thus, how the subunit composition of heterotetrameric IP3R channels contributes to shaping the spatio-temporal properties of IP3-mediated Ca(2+) signals has been difficult to evaluate. To address this question, we created concatenated IP3R linked by short flexible linkers. Dimeric constructs were expressed in DT40-3KO cells, an IP3R null cell line. The dimeric proteins were localized to membranes, ran as intact dimeric proteins on SDS-PAGE, and migrated as an ∼1100-kDa band on blue native gels exactly as wild type IP3R. Importantly, IP3R channels formed from concatenated dimers were fully functional as indicated by agonist-induced Ca(2+) release. Using single channel "on-nucleus" patch clamp, the channels assembled from homodimers were essentially indistinguishable from those formed by the wild type receptor. However, the activity of channels formed from concatenated IP3R1 and IP3R2 heterodimers was dominated by IP3R2 in terms of the characteristics of regulation by ATP. These studies provide the first insight into the regulation of heterotetrameric IP3R of defined composition. Importantly, the results indicate that the properties of these channels are not simply a blend of those of the constituent IP3R monomers.
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Affiliation(s)
- Kamil J Alzayady
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
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Turovsky EA, Turovskaya MV, Dolgacheva LP, Zinchenko VP, Dynnik VV. Acetylcholine promotes Ca2+ and NO-oscillations in adipocytes implicating Ca2+→NO→cGMP→cADP-ribose→Ca2+ positive feedback loop--modulatory effects of norepinephrine and atrial natriuretic peptide. PLoS One 2013; 8:e63483. [PMID: 23696827 PMCID: PMC3656004 DOI: 10.1371/journal.pone.0063483] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 04/03/2013] [Indexed: 02/05/2023] Open
Abstract
PURPOSE This study investigated possible mechanisms of autoregulation of Ca(2+) signalling pathways in adipocytes responsible for Ca(2+) and NO oscillations and switching phenomena promoted by acetylcholine (ACh), norepinephrine (NE) and atrial natriuretic peptide (ANP). METHODS Fluorescent microscopy was used to detect changes in Ca(2+) and NO in cultures of rodent white adipocytes. Agonists and inhibitors were applied to characterize the involvement of various enzymes and Ca(2+)-channels in Ca(2+) signalling pathways. RESULTS ACh activating M3-muscarinic receptors and Gβγ protein dependent phosphatidylinositol 3 kinase induces Ca(2+) and NO oscillations in adipocytes. At low concentrations of ACh which are insufficient to induce oscillations, NE or α1, α2-adrenergic agonists act by amplifying the effect of ACh to promote Ca(2+) oscillations or switching phenomena. SNAP, 8-Br-cAMP, NAD and ANP may also produce similar set of dynamic regimes. These regimes arise from activation of the ryanodine receptor (RyR) with the implication of a long positive feedback loop (PFL): Ca(2+)→NO→cGMP→cADPR→Ca(2+), which determines periodic or steady operation of a short PFL based on Ca(2+)-induced Ca(2+) release via RyR by generating cADPR, a coagonist of Ca(2+) at the RyR. Interplay between these two loops may be responsible for the observed effects. Several other PFLs, based on activation of endothelial nitric oxide synthase or of protein kinase B by Ca(2+)-dependent kinases, may reinforce functioning of main PFL and enhance reliability. All observed regimes are independent of operation of the phospholipase C/Ca(2+)-signalling axis, which may be switched off due to negative feedback arising from phosphorylation of the inositol-3-phosphate receptor by protein kinase G. CONCLUSIONS This study presents a kinetic model of Ca(2+)-signalling system operating in adipocytes and integrating signals from various agonists, which describes it as multivariable multi feedback network with a family of nested positive feedback.
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Affiliation(s)
- Egor A. Turovsky
- Department of Intracellular Signalling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
| | - Mariya V. Turovskaya
- Department of Intracellular Signalling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
| | - Ludmila P. Dolgacheva
- Department of Intracellular Signalling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
| | - Valery P. Zinchenko
- Department of Intracellular Signalling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
| | - Vladimir V. Dynnik
- Department of Intracellular Signalling, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
- Department of System Biochemistry, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Russia
- * E-mail:
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The antiplatelet activity of magnolol is mediated by PPAR-β/γ. Biochem Pharmacol 2012; 84:793-803. [PMID: 22750553 DOI: 10.1016/j.bcp.2012.06.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Revised: 06/13/2012] [Accepted: 06/21/2012] [Indexed: 11/20/2022]
Abstract
Activation of peroxisome proliferator-activated receptor (PPAR) isoforms (α, β/δ, and γ) is known to inhibit platelet aggregation. In the present study, we examined whether PPARs-mediated pathways contribute to the antiplatelet activity of magnolol, a compound purified from Magnolia officinalis. Magnolol (20-60 μM) dose-dependently enhanced the activity and intracellular level of PPAR-β/γ in platelets. In the presence of selective PPAR-β antagonist (GSK0660) or PPAR-γ antagonist (GW9662), the inhibition of magnolol on collagen-induced platelet aggregation and intracellular Ca(2+) mobilization was significantly reversed. Moreover, magnolol-mediated up-regulation of NO/cyclic GMP/PKG pathway and Akt phosphorylation leading to increase of eNOS activity were markedly abolished by blocking PPAR-β/γ activity. Additionally, magnolol significantly inhibited collagen-induced PKCα activation through a PPAR-β/γ and PKCα interaction manner. The arachidonic acid (AA) or collagen-induced thromboxane B(2) formation and elevation of COX-1 activity caused by AA were also markedly attenuated by magnolol. However, these above effects of magnolol on platelet responses were strongly reduced by simultaneous addition of GSK0660 or GW9662, suggesting that PPAR-β/γ-mediated processes may account for magnolol-regulated antiplatelet mechanisms. Similarly, administration of PPAR-β/γ antagonists remarkably abolished the actions of magnolol in preventing platelet plug formation and prolonging bleeding time in mice. Taken together, we demonstrate for the first time that the antiplatelet and anti-thrombotic activities of magnolol are modulated by up-regulation of PPAR-β/γ-dependent pathways.
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Abstract
Signaling by nitric oxide (NO) determines several cardiovascular functions including blood pressure regulation, cardiac and smooth muscle hypertrophy, and platelet function. NO stimulates the synthesis of cGMP by soluble guanylyl cyclases and thereby activates cGMP-dependent protein kinases (PKGs), mediating most of the cGMP functions. Hence, an elucidation of the PKG signaling cascade is essential for the understanding of the (patho)physiological aspects of NO. Several PKG signaling pathways were identified, meanwhile regulating the intracellular calcium concentration, mediating calcium desensitization or cytoskeletal rearrangement. During the last decade it emerged that the inositol trisphosphate receptor-associated cGMP-kinase substrate (IRAG), an endoplasmic reticulum-anchored 125-kDa membrane protein, is a main signal transducer of PKG activity in the cardiovascular system. IRAG interacts specifically in a trimeric complex with the PKG1β isoform and the inositol 1,4,5-trisphosphate receptor I and, upon phosphorylation, reduces the intracellular calcium release from the intracellular stores. IRAG motifs for phosphorylation and for targeting to PKG1β and 1,4,5-trisphosphate receptor I were identified by several approaches. The (patho)physiological functions for the regulation of smooth muscle contractility and the inhibition of platelet activation were perceived. In this review, the IRAG recognition, targeting, and function are summarized compared with PKG and several PKG substrates in the cardiovascular system.
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Affiliation(s)
- Jens Schlossmann
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Regensburg, Regensburg, Germany.
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