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Bird GS, Lin YP, Tucker CJ, Mueller G, Shi M, Padmanabhan S, Parekh AB. Scrutinizing science to save lives: uncovering flaws in the data linking L-type calcium channels blockers to CRAC channels and heart failure. bioRxiv 2024:2024.02.06.579229. [PMID: 38370647 PMCID: PMC10871304 DOI: 10.1101/2024.02.06.579229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Hypertension is estimated to affect almost 1 billion people globally and significantly increases risk of myocardial infarction, heart failure, stroke, retinopathy and kidney disease. One major front line therapy that has been used for over 50 years involves L-type Ca 2+ channel blockers (LCCBs). One class of LCCBs is the dihydropyridine family, with amlodipine being widely prescribed regardless of gender, race, ethnicity or age. In 2020, Johnson et al. 7 reported that all LCCBs significantly increased the risk of heart failure, and attributed this effect to non-canonical activation of store-operated Ca 2+ entry. A major approach on which they based many of their arguments was to measure cytosolic Ca 2+ using the fluorescent Ca 2+ indicator dye fura-2. We recently demonstrated that amlodipine is highly fluorescent within cells and overwhelms the fura-2 signal, precluding the use of the indicator dye with amlodipine 24 . Our meta-analyses and prospective real world study showed that dihydropyridines were not associated with an increase in heart failure, likely explained by the lack of consideration by Johnson et al. 7 of well-known confounding factors such as age, race, obesity, prior anti-hypertensive treatment or diabetes 24 . Trebak and colleagues have responded to our paper with a forthright and unwavering defence of their work 27 . In this paper, we carry out a forensic dissection of Johnson et al., 7 and conduct new experiments that address directly points raised by Trebak et al. 27 . We show that there are major flaws in the design and interpretation of their key experiments, that fura-2 cannot be used with amlodipine, that there are fundamental mathematical misunderstandings and mistakes throughout their study leading to critical calculations on heart failure that are demonstrably wrong, and several of their own results are inconsistent with their interpretation. We therefore believe the study by Johnson et al. 7 is flawed at many levels and we stand by our conclusions.
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Parekh AB. House dust mite allergens, store-operated Ca 2+ channels and asthma. J Physiol 2023. [PMID: 38054814 DOI: 10.1113/jp284931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 10/26/2023] [Indexed: 12/07/2023] Open
Abstract
The house dust mite is the principal source of aero-allergen worldwide. Exposure to mite-derived allergens is associated with the development of asthma in susceptible individuals, and the majority of asthmatics are allergic to the mite. Mite-derived allergens are functionally diverse and activate multiple cell types within the lung that result in chronic inflammation. Allergens activate store-operated Ca2+ release-activated Ca2+ (CRAC) channels, which are widely expressed in multiple cell types within the lung that are associated with the pathogenesis of asthma. Opening of CRAC channels stimulates Ca2+ -dependent transcription factors, including nuclear factor of activated T cells and nuclear factor-κB, which drive expression of a plethora of pro-inflammatory cytokines and chemokines that help to sustain chronic inflammation. Here, I describe drivers of asthma, properties of mite-derived allergens, how the allergens are recognized by cells, the signalling pathways used by the receptors and how these are transduced into functional effects, with a focus on CRAC channels. In vivo experiments that demonstrate the effectiveness of targeting CRAC channels as a potential new therapy for treating mite-induced asthma are also discussed, in tandem with other possible approaches.
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Affiliation(s)
- Anant B Parekh
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, Research Triangle Park, Durham, NC, USA
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3
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Bird GS, D’Agostin D, Alsanosi S, Lip S, Padmanabhan S, Parekh AB. A Reappraisal of the Effects of L-type Ca 2+ Channel Blockers on Store-Operated Ca 2+ Entry and Heart Failure. Function (Oxf) 2023; 4:zqad047. [PMID: 37841523 PMCID: PMC10568199 DOI: 10.1093/function/zqad047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 08/06/2023] [Indexed: 10/17/2023] Open
Abstract
Dihydropyridines such as amlodipine are widely used as antihypertensive agents, being prescribed to ∼70 million Americans and >0.4 billion adults worldwide. Dihydropyridines block voltage-gated Ca2+ channels in resistance vessels, leading to vasodilation and a reduction in blood pressure. Various meta-analyses show that dihydropyridines are relatively safe and effective in reducing hypertension. The use of dihydropyridines has recently been called into question as these drugs appear to activate store-operated Ca2+ entry in fura-2-loaded nonexcitable cells, trigger vascular remodeling, and increase heart failure, leading to the questioning of their clinical use. Given that hypertension is the dominant "silent killer" across the globe affecting ∼1.13 billion people, removal of Ca2+ channel blockers as antihypertensive agents has major health implications. Here, we show that amlodipine has marked intrinsic fluorescence, which further increases considerably inside cells over an identical excitation spectrum as fura-2, confounding the ability to measure cytosolic Ca2+. Using longer wavelength Ca2+ indicators, we find that concentrations of Ca2+ channel blockers that match therapeutic levels in serum of patients do not activate store-operated Ca2+ entry. Antihypertensive Ca2+ channel blockers at pharmacological concentrations either have no effect on store-operated channels, activate them indirectly through store depletion or inhibit the channels. Importantly, a meta-analysis of published clinical trials and a prospective real-world analysis of patients prescribed single antihypertensive agents for 6 mo and followed up 1 yr later both show that dihydropyridines are not associated with increased heart failure or other cardiovascular disorders. Removal of dihydropyridines for treatment of hypertension cannot therefore be recommended.
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Affiliation(s)
- Gary S Bird
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Diane D’Agostin
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Safaa Alsanosi
- BHF Glasgow Cardiovascular Research Centre, School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow G12 8TA, UK
- Department of Pharmacology and Toxicology, Faculty of Medicine, Umm Al Qura University, P.O. Box 715, Makkah 21955, Saudi Arabia
| | - Stefanie Lip
- BHF Glasgow Cardiovascular Research Centre, School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow G12 8TA, UK
| | - Sandosh Padmanabhan
- BHF Glasgow Cardiovascular Research Centre, School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow G12 8TA, UK
| | - Anant B Parekh
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
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Parekh AB, Parekh LBC. "Study the Past if You Would Define the Future."-Confucius. Function (Oxf) 2023; 4:zqac073. [PMID: 36686642 PMCID: PMC9850269 DOI: 10.1093/function/zqac073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Accepted: 12/28/2022] [Indexed: 01/15/2023]
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Barak P, Kaur S, Scappini E, Tucker CJ, Parekh AB. Plasma Membrane Ca2+ ATPase Activity Enables Sustained Store-operated Ca2+ Entry in the Absence of a Bulk Cytosolic Ca2+ Rise. Function 2022. [DOI: 10.1093/function/zqac040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
In many cell types, the rise in cytosolic Ca2+ due to opening of Ca2+ release-activated Ca2+ (CRAC) channels drives a plethora of responses, including secretion, motility, energy production, and gene expression. The amplitude and time course of the cytosolic Ca2+ rise is shaped by the rates of Ca2+ entry into and removal from the cytosol. However, an extended bulk Ca2+ rise is toxic to cells. Here, we show that the plasma membrane Ca2+ ATPase (PMCA) pump plays a major role in preventing a prolonged cytosolic Ca2+ signal following CRAC channel activation. Ca2+ entry through CRAC channels leads to a sustained sub-plasmalemmal Ca2+ rise but bulk Ca2+ is kept low by the activity of PMCA4b. Despite the low cytosolic Ca2+, membrane permeability to Ca2+ is still elevated and Ca2+ continues to enter through CRAC channels. Ca2+-dependent NFAT activation, driven by Ca2+ nanodomains near the open channels, is maintained despite the return of bulk Ca2+ to near pre-stimulation levels. Our data reveal a central role for PMCA4b in determining the pattern of a functional Ca2+ signal and in sharpening local Ca2+ gradients near CRAC channels, whilst protecting cells from a toxic Ca2+ overload.
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Affiliation(s)
- Pradeep Barak
- Department of Physiology, Anatomy and Genetics, Oxford University , Oxford OX1 3PT, UK
- Oxford Nanoimaging , Linacre House, Jordan Hill Business Park Banbury Road, Oxford OX2 8TA, UK
| | - Suneet Kaur
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences , NIH, Research Triangle Park NC 27709, USA
| | - Erica Scappini
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences , NIH, Research Triangle Park NC 27709, USA
| | - Charles J Tucker
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences , NIH, Research Triangle Park NC 27709, USA
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University , Oxford OX1 3PT, UK
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences , NIH, Research Triangle Park NC 27709, USA
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Yeh YC, Lin YP, Kramer H, Parekh AB. Single-nucleotide polymorphisms in Orai1 associated with atopic dermatitis inhibit protein turnover, decrease calcium entry and disrupt calcium-dependent gene expression. Hum Mol Genet 2021; 29:1808-1823. [PMID: 31600783 PMCID: PMC7372555 DOI: 10.1093/hmg/ddz223] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/10/2019] [Accepted: 08/12/2019] [Indexed: 12/23/2022] Open
Abstract
Loss-of function mutations in Orai1 Ca2+ channels lead to a form of severe combined immunodeficiency, auto-immunity, muscle hypotonia and defects in dental enamel production and sweat gland function. Two single-nucleotide polymorphisms (SNPs) in Orai1 have been found and localize to the second extracellular loop. These polymorphisms associate with atopic dermatitis but how they affect Ca2+ signalling and cell function is unknown. Here, we find that Orai1–SNPs turnover considerably more slowly than wild type Orai1 and are more abundantly expressed in the plasma membrane. We show a central role for flotillin in the endocytotic recycling of Orai1 channels and that endocytosed wild type Orai1 is trafficked to Rab 7-positive late endosomes for lysosomal degradation. Orai1–SNPs escape the degradation pathway and instead enter Rab 11-positive recycling endosomes, where they are returned to the surface membrane through Arf6-dependent exocytosis. We find that Orai1–SNPs escape late endosomes through endosomal pH regulation of interaction between the channel and flotillin. We identify a pH-sensitive electrostatic interaction between positively charged arginine in extracellular loop 2 (K210) and a negatively charged aspartate (D112) in extracellular loop 1 that helps determine Orai1 turnover. The increase in membrane Orai1–SNP leads to a mis-match in Orai1–STIM stoichiometry, resulting in inhibition of Ca2+ entry and Ca2+-dependent gene expression. Our results identify new strategies for targeting atopic dermatitis.
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Affiliation(s)
- Yi-Chun Yeh
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford, OX1 3PT UK
| | - Yu-Ping Lin
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford, OX1 3PT UK
| | - Holger Kramer
- MRC London Institute of Medical Sciences, Imperial College London, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford, OX1 3PT UK
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Kar P, Barak P, Zerio A, Lin YP, Parekh AJ, Watts VJ, Cooper DMF, Zaccolo M, Kramer H, Parekh AB. AKAP79 Orchestrates a Cyclic AMP Signalosome Adjacent to Orai1 Ca 2+ Channels. Function (Oxf) 2021; 2:zqab036. [PMID: 34458850 PMCID: PMC8394516 DOI: 10.1093/function/zqab036] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/16/2021] [Accepted: 07/27/2021] [Indexed: 01/12/2023]
Abstract
To ensure specificity of response, eukaryotic cells often restrict signalling molecules to sub-cellular regions. The Ca2+ nanodomain is a spatially confined signal that arises near open Ca2+ channels. Ca2+ nanodomains near store-operated Orai1 channels stimulate the protein phosphatase calcineurin, which activates the transcription factor NFAT1, and both enzyme and target are initially attached to the plasma membrane through the scaffolding protein AKAP79. Here, we show that a cAMP signalling nexus also forms adjacent to Orai1. Protein kinase A and phosphodiesterase 4, an enzyme that rapidly breaks down cAMP, both associate with AKAP79 and realign close to Orai1 after stimulation. PCR and mass spectrometry failed to show expression of Ca2+-activated adenylyl cyclase 8 in HEK293 cells, whereas the enzyme was observed in neuronal cell lines. FRET and biochemical measurements of bulk cAMP and protein kinase A activity consistently failed to show an increase in adenylyl cyclase activity following even a large rise in cytosolic Ca2+. Furthermore, expression of AKAP79-CUTie, a cAMP FRET sensor tethered to AKAP79, did not report a rise in cAMP after stimulation, despite AKAP79 association with Orai1. Hence, HEK293 cells do not express functional active Ca2+-activated adenylyl cyclases including adenylyl cyclase 8. Our results show that two ancient second messengers are independently generated in nanodomains close to Orai1 Ca2+ channels.
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Affiliation(s)
- Pulak Kar
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Pradeep Barak
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Anna Zerio
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Yu-Ping Lin
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK,NIEHS/NIH, 111 TW Alexander Drive, Durham, NC 27709, USA
| | - Amy J Parekh
- Stoke Mandeville Hospital, Mandeville Road, Aylesbury, HP21 8AL, UK
| | - Val J Watts
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue Institute of Drug Discovery, Purdue Institute of Neuroscience, Purdue University, West Lafayette, IN 47907, USA
| | - Dermot M F Cooper
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Holger Kramer
- Proteomics and Metabolomics Centre, Medical Research Council, London Institute of Medical Sciences, London, W12 0NN, UK
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8
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Kar P, Lin YP, Bhardwaj R, Tucker CJ, Bird GS, Hediger MA, Monico C, Amin N, Parekh AB. The N terminus of Orai1 couples to the AKAP79 signaling complex to drive NFAT1 activation by local Ca 2+ entry. Proc Natl Acad Sci U S A 2021; 118:e2012908118. [PMID: 33941685 PMCID: PMC8126794 DOI: 10.1073/pnas.2012908118] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To avoid conflicting and deleterious outcomes, eukaryotic cells often confine second messengers to spatially restricted subcompartments. The smallest signaling unit is the Ca2+ nanodomain, which forms when Ca2+ channels open. Ca2+ nanodomains arising from store-operated Orai1 Ca2+ channels stimulate the protein phosphatase calcineurin to activate the transcription factor nuclear factor of activated T cells (NFAT). Here, we show that NFAT1 tethered directly to the scaffolding protein AKAP79 (A-kinase anchoring protein 79) is activated by local Ca2+ entry, providing a mechanism to selectively recruit a transcription factor. We identify the region on the N terminus of Orai1 that interacts with AKAP79 and demonstrate that this site is essential for physiological excitation-transcription coupling. NMR structural analysis of the AKAP binding domain reveals a compact shape with several proline-driven turns. Orai2 and Orai3, isoforms of Orai1, lack this region and therefore are less able to engage AKAP79 and activate NFAT. A shorter, naturally occurring Orai1 protein that arises from alternative translation initiation also lacks the AKAP79-interaction site and fails to activate NFAT1. Interfering with Orai1-AKAP79 interaction suppresses cytokine production, leaving other Ca2+ channel functions intact. Our results reveal the mechanistic basis for how a subtype of a widely expressed Ca2+ channel is able to activate a vital transcription pathway and identify an approach for generation of immunosuppressant drugs.
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Affiliation(s)
- Pulak Kar
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford OX1 3PT, United Kingdom
| | - Yu-Ping Lin
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford OX1 3PT, United Kingdom
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709
| | - Rajesh Bhardwaj
- Department of Nephrology and Hypertension, University Hospital Bern, Inselspital, 3010 Bern, Switzerland
| | - Charles J Tucker
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709
| | - Gary S Bird
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709
| | - Matthias A Hediger
- Department of Nephrology and Hypertension, University Hospital Bern, Inselspital, 3010 Bern, Switzerland
| | - Carina Monico
- Micron Oxford Advanced Bioimaging Unit, Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom
| | - Nader Amin
- Department of Chemistry, Oxford University, Oxford OX1 3TA, United Kingdom
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford OX1 3PT, United Kingdom;
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709
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9
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Parekh AB. Opening New Terrain in Intracellular Ca 2+ Signaling. Function (Oxf) 2021; 2:zqab016. [PMID: 35330677 PMCID: PMC8788851 DOI: 10.1093/function/zqab016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 03/11/2021] [Accepted: 03/12/2021] [Indexed: 01/06/2023] Open
Affiliation(s)
- Anant B Parekh
- Laboratory of Signal Transduction, National Institute of Environmental Health, Sciences, National Institutes of Health, NC 27709, USA
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10
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Bakowski D, Wood AJ, Parekh AB. Sequi Ad Maius Bonum; Targeting Ion Channels in the Lung. Function (Oxf) 2020; 2:zqaa045. [PMID: 34223171 PMCID: PMC8248880 DOI: 10.1093/function/zqaa045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 12/18/2020] [Indexed: 01/06/2023]
Affiliation(s)
| | | | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford, OX1 3PT, UK,Address correspondence to A.B.P. (e-mail: )
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11
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Abstract
Calcium (Ca2+) release-activated Ca2+ (CRAC) channels are a major route for Ca2+ entry in eukaryotic cells. These channels are store operated, opening when the endoplasmic reticulum (ER) is depleted of Ca2+, and are composed of the ER Ca2+ sensor protein STIM and the pore-forming plasma membrane subunit Orai. Recent years have heralded major strides in our understanding of the structure, gating, and function of the channels. Loss-of-function and gain-of-function mutants combined with RNAi knockdown strategies have revealed important roles for the channel in numerous human diseases, making the channel a clinically relevant target. Drugs targeting the channels generally lack specificity or exhibit poor efficacy in animal models. However, the landscape is changing, and CRAC channel blockers are now entering clinical trials. Here, we describe the key molecular and biological features of CRAC channels, consider various diseases associated with aberrant channel activity, and discuss targeting of the channels from a therapeutic perspective.
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Affiliation(s)
| | - Fraser Murray
- Pandeia Therapeutics, Oxford OX4 4GP, United Kingdom
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford OX1 3PT, United Kingdom; , .,Current affiliation: National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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12
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Abstract
Calcium (Ca2+) ion microdomains are subcellular regions of high Ca2+ concentration that develop rapidly near open Ca2+ channels in the plasma membrane or internal stores and generate local regions of high Ca2+ concentration. These microdomains are remarkably versatile in that they activate a range of responses that differ enormously in both their temporal and spatial profile. In this review, we describe how Ca2+ microdomains generated by store-operated calcium channels, a widespread and conserved Ca2+ entry pathway, stimulate different signaling pathways, and how the spatial extent of a Ca2+ microdomain can be influenced by Ca2+ ATPase pumps.
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Affiliation(s)
- Pradeep Barak
- Department of Physiology, Anatomy, and Genetics, Oxford University, Oxford OX1 3PT, United Kingdom
| | - Anant B Parekh
- Department of Physiology, Anatomy, and Genetics, Oxford University, Oxford OX1 3PT, United Kingdom
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13
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Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, OX1 3PT, UK.
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14
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Lin YP, Bakowski D, Mirams GR, Parekh AB. Selective recruitment of different Ca 2+-dependent transcription factors by STIM1-Orai1 channel clusters. Nat Commun 2019; 10:2516. [PMID: 31175287 PMCID: PMC6555828 DOI: 10.1038/s41467-019-10329-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 04/23/2019] [Indexed: 11/08/2022] Open
Abstract
Store-operated Ca2+ entry, involving endoplasmic reticulum Ca2+ sensing STIM proteins and plasma membrane Orai1 channels, is a widespread and evolutionary conserved Ca2+ influx pathway. This form of Ca2+ influx occurs at discrete loci where peripheral endoplasmic reticulum juxtaposes the plasma membrane. Stimulation evokes numerous STIM1-Orai1 clusters but whether distinct signal transduction pathways require different cluster numbers is unknown. Here, we show that two Ca2+-dependent transcription factors, NFAT1 and c-fos, have different requirements for the number of STIM1-Orai1 clusters and on the Ca2+ flux through them. NFAT activation requires fewer clusters and is more robustly activated than c-fos by low concentrations of agonist. For similar cluster numbers, transcription factor recruitment occurs sequentially, arising from intrinsic differences in Ca2+ sensitivities. Variations in the number of STIM1-Orai1 clusters and Ca2+ flux through them regulate the robustness of signalling to the nucleus whilst imparting a mechanism for selective recruitment of different Ca2+-dependent transcription factors.
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Affiliation(s)
- Yu-Ping Lin
- Department of Physiology, Anatomy and Genetics, Oxford University, Parks Road, Oxford, OX1 3PT, UK
| | - Daniel Bakowski
- Department of Physiology, Anatomy and Genetics, Oxford University, Parks Road, Oxford, OX1 3PT, UK
| | - Gary R Mirams
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, Nottingham University, Nottingham, NG7 2RD, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University, Parks Road, Oxford, OX1 3PT, UK.
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15
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Samanta K, Bakowski D, Amin N, Parekh AB. The whole-cell Ca 2+ release-activated Ca 2+ current, I CRAC , is regulated by the mitochondrial Ca 2+ uniporter channel and is independent of extracellular and cytosolic Na . J Physiol 2019; 598:1753-1773. [PMID: 30582626 PMCID: PMC7318671 DOI: 10.1113/jp276551] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 12/05/2018] [Indexed: 12/12/2022] Open
Abstract
Key points Ca2+ entry through Ca2+ release‐activated Ca2+ channels activates numerous cellular responses. Under physiological conditions of weak intracellular Ca2+ buffering, mitochondrial Ca2+ uptake regulates CRAC channel activity. Knockdown of the mitochondrial Ca2+ uniporter channel prevented the development of ICRAC in weak buffer but not when strong buffer was used instead. Removal of either extracellular or intra‐pipette Na+ had no effect on the selectivity, kinetics, amplitude, rectification or reversal potential of whole‐cell CRAC current. Knockdown of the mitochondrial Na+–Ca2+ exchanger did not prevent the development of ICRAC in strong or weak Ca2+ buffer. Whole cell CRAC current is Ca2+‐selective. Mitochondrial Ca2+ channels, and not Na+‐dependent transport, regulate CRAC channels under physiological conditions.
Abstract Ca2+ entry through store‐operated Ca2+ release‐activated Ca2+ (CRAC) channels plays a central role in activation of a range of cellular responses over broad spatial and temporal bandwidths. Mitochondria, through their ability to take up cytosolic Ca2+, are important regulators of CRAC channel activity under physiological conditions of weak intracellular Ca2+ buffering. The mitochondrial Ca2+ transporter(s) that regulates CRAC channels is unclear and could involve the 40 kDa mitochondrial Ca2+ uniporter (MCU) channel or the Na+–Ca2+–Li+ exchanger (NCLX). Here, we have investigated the involvement of these mitochondrial Ca2+ transporters in supporting the CRAC current (ICRAC) under a range of conditions in RBL mast cells. Knockdown of the MCU channel impaired the activation of ICRAC under physiological conditions of weak intracellular Ca2+ buffering. In strong Ca2+ buffer, knockdown of the MCU channel did not inhibit ICRAC development demonstrating that mitochondria regulate CRAC channels under physiological conditions by buffering of cytosolic Ca2+ via the MCU channel. Surprisingly, manipulations that altered extracellular Na+, cytosolic Na+ or both failed to inhibit the development of ICRAC in either strong or weak intracellular Ca2+ buffer. Knockdown of NCLX also did not affect ICRAC. Prolonged removal of external Na+ also had no significant effect on store‐operated Ca2+ entry, on cytosolic Ca2+ oscillations generated by receptor stimulation or on CRAC channel‐driven gene expression. In the RBL mast cell, Ca2+ flux through the MCU but not NCLX is indispensable for activation of ICRAC. Ca2+ entry through Ca2+ release‐activated Ca2+ channels activates numerous cellular responses. Under physiological conditions of weak intracellular Ca2+ buffering, mitochondrial Ca2+ uptake regulates CRAC channel activity. Knockdown of the mitochondrial Ca2+ uniporter channel prevented the development of ICRAC in weak buffer but not when strong buffer was used instead. Removal of either extracellular or intra‐pipette Na+ had no effect on the selectivity, kinetics, amplitude, rectification or reversal potential of whole‐cell CRAC current. Knockdown of the mitochondrial Na+–Ca2+ exchanger did not prevent the development of ICRAC in strong or weak Ca2+ buffer. Whole cell CRAC current is Ca2+‐selective. Mitochondrial Ca2+ channels, and not Na+‐dependent transport, regulate CRAC channels under physiological conditions.
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Affiliation(s)
- Krishna Samanta
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Daniel Bakowski
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Nader Amin
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
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16
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Lin YP, Nelson C, Kramer H, Parekh AB. The Allergen Der p3 from House Dust Mite Stimulates Store-Operated Ca 2+ Channels and Mast Cell Migration through PAR4 Receptors. Mol Cell 2019; 70:228-241.e5. [PMID: 29677491 DOI: 10.1016/j.molcel.2018.03.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 02/05/2018] [Accepted: 03/22/2018] [Indexed: 11/17/2022]
Abstract
The house dust mite is the principal source of perennial aeroallergens in man. How these allergens activate innate and adaptive immunity is unclear, and therefore, there are no therapies targeting mite allergens. Here, we show that house dust mite extract activates store-operated Ca2+ channels, a common signaling module in numerous cell types in the lung. Activation of channel pore-forming Orai1 subunits by mite extract requires gating by STIM1 proteins. Although mite extract stimulates both protease-activated receptor type 2 (PAR2) and PAR4 receptors, Ca2+ influx is more tightly coupled to the PAR4 pathway. We identify a major role for the serine protease allergen Der p3 in stimulating Orai1 channels and show that a therapy involving sub-maximal inhibition of both Der p3 and Orai1 channels suppresses mast cell activation to house dust mite. Our results reveal Der p3 as an important aeroallergen that activates Ca2+ channels and suggest a therapeutic strategy for treating mite-induced asthma.
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Affiliation(s)
- Yu-Ping Lin
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Charmaine Nelson
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Holger Kramer
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
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17
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Affiliation(s)
- Andrea Fleig
- The Queen's Medical Center and John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford, OX1 3PT, UK
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18
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Samanta K, Parekh AB. Store-operated Ca2+ channels in airway epithelial cell function and implications for asthma. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0424. [PMID: 27377718 PMCID: PMC4938024 DOI: 10.1098/rstb.2015.0424] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2016] [Indexed: 12/18/2022] Open
Abstract
The epithelial cells of the lung are at the interface of a host and its environment and are therefore directly exposed to the inhaled air-borne particles. Rather than serving as a simple physical barrier, airway epithelia detect allergens and other irritants and then help organize the subsequent immune response through release of a plethora of secreted signals. Many of these signals are generated in response to opening of store-operated Ca2+ channels in the plasma membrane. In this review, we describe the properties of airway store-operated channels and their role in regulating airway epithelial cell function. This article is part of the themed issue ‘Evolution brings Ca2+ and ATP together to control life and death’.
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Affiliation(s)
- Krishna Samanta
- Department of Physiology, Anatomy and Genetics, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
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19
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Kar P, Mirams GR, Christian HC, Parekh AB. Control of NFAT Isoform Activation and NFAT-Dependent Gene Expression through Two Coincident and Spatially Segregated Intracellular Ca 2+ Signals. Mol Cell 2017; 64:746-759. [PMID: 27863227 PMCID: PMC5128683 DOI: 10.1016/j.molcel.2016.11.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 08/22/2016] [Accepted: 11/03/2016] [Indexed: 01/25/2023]
Abstract
Excitation-transcription coupling, linking stimulation at the cell surface to changes in nuclear gene expression, is conserved throughout eukaryotes. How closely related coexpressed transcription factors are differentially activated remains unclear. Here, we show that two Ca2+-dependent transcription factor isoforms, NFAT1 and NFAT4, require distinct sub-cellular InsP3 and Ca2+ signals for physiologically sustained activation. NFAT1 is stimulated by sub-plasmalemmal Ca2+ microdomains, whereas NFAT4 additionally requires Ca2+ mobilization from the inner nuclear envelope by nuclear InsP3 receptors. NFAT1 is rephosphorylated (deactivated) more slowly than NFAT4 in both cytoplasm and nucleus, enabling a more prolonged activation phase. Oscillations in cytoplasmic Ca2+, long considered the physiological form of Ca2+ signaling, play no role in activating either NFAT protein. Instead, effective sustained physiological activation of NFAT4 is tightly linked to oscillations in nuclear Ca2+. Our results show how gene expression can be controlled by coincident yet geographically distinct Ca2+ signals, generated by a freely diffusible InsP3 message. NFAT1 is activated by local Ca2+ entry, whereas NFAT4 also needs nuclear Ca2+ Nuclear Ca2+ increases via InsP3 receptors located on the inner nuclear membrane NFAT1 and NFAT4 show very different rephosphorylation (deactivation) kinetics Slow deactivation of NFAT1 affords a form of short-term memory to gene expression
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Affiliation(s)
- Pulak Kar
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Gary R Mirams
- Computational Biology, Department of Computer Science, University of Oxford, Parks Road, Oxford, OX1 3QD, UK
| | - Helen C Christian
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK.
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20
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Samanta K, Parekh AB. Spatial Ca 2+ profiling: decrypting the universal cytosolic Ca 2+ oscillation. J Physiol 2016; 595:3053-3062. [PMID: 27859266 DOI: 10.1113/jp272860] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 11/04/2016] [Indexed: 01/11/2023] Open
Abstract
Stimulation of cell-surface receptors that couple to phospholipase C to generate the second messenger inositol trisphosphate often evokes repetitive oscillations in cytosolic Ca2+ . Signalling information is encoded in both the amplitude and frequency of the Ca2+ spikes. Recent studies have revealed that the spatial profile of the oscillation also imparts signalling power; Ca2+ microdomains near store-operated CRAC channels in the plasma membrane and inositol trisphosphate-gated channels in the endoplasmic reticulum both signal to distinct downstream targets. Spatial profiling therefore increases the transduction power of the universal oscillatory cytosolic Ca2+ signal.
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Affiliation(s)
- Krishna Samanta
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
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21
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Abstract
CRAC channels are a major route for Ca2+ influx in eukaryotic cells. The channels show prominent Ca2+-dependent inactivation through two spatially and temporally distinct mechanisms: fast inactivation, which develops over milliseconds and is triggered by Ca2+ near the mouth of the channel and slow inactivation, which arises over tens of seconds and requires a rise in global cytosolic Ca2+. Slow inactivation is controlled physiologically by Ca2+ uptake into mitochondria through the MCU. Site-directed mutagenesis studies on STIM1 and Orai1 have led to new molecular insight into how fast inactivation occurs. This review describes properties and molecular mechanisms that contribute to these important Ca2+-dependent inhibitory pathways.
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Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Parks Road Oxford OX1 3PT, UK.
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22
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Parekh AB. Advances in intracellular Ca(2+) signalling. J Physiol 2016; 594:2811-2. [PMID: 27246547 DOI: 10.1113/jp272230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 03/06/2016] [Indexed: 11/08/2022] Open
Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK
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23
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Alswied A, Parekh AB. Ca2+ Influx through Store-operated Calcium Channels Replenishes the Functional Phosphatidylinositol 4,5-Bisphosphate Pool Used by Cysteinyl Leukotriene Type I Receptors. J Biol Chem 2015; 290:29555-66. [PMID: 26468289 PMCID: PMC4705955 DOI: 10.1074/jbc.m115.678292] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Indexed: 11/06/2022] Open
Abstract
Oscillations in cytoplasmic Ca2+ concentration are a universal mode of signaling following physiological levels of stimulation with agonists that engage the phospholipase C pathway. Sustained cytoplasmic Ca2+ oscillations require replenishment of the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2), the source of the Ca2+-releasing second messenger inositol trisphosphate. Here we show that cytoplasmic Ca2+ oscillations induced by cysteinyl leukotriene type I receptor activation run down when cells are pretreated with Li+, an inhibitor of inositol monophosphatases that prevents PIP2 resynthesis. In Li+-treated cells, cytoplasmic Ca2+ signals evoked by an agonist were rescued by addition of exogenous inositol or phosphatidylinositol 4-phosphate (PI4P). Knockdown of the phosphatidylinositol 4-phosphate 5 (PIP5) kinases α and γ resulted in rapid loss of the intracellular Ca2+ oscillations and also prevented rescue by PI4P. Knockdown of talin1, a protein that helps regulate PIP5 kinases, accelerated rundown of cytoplasmic Ca2+ oscillations, and these could not be rescued by inositol or PI4P. In Li+-treated cells, recovery of the cytoplasmic Ca2+ oscillations in the presence of inositol or PI4P was suppressed when Ca2+ influx through store-operated Ca2+ channels was inhibited. After rundown of the Ca2+ signals following leukotriene receptor activation, stimulation of P2Y receptors evoked prominent inositol trisphosphate-dependent Ca2+ release. Therefore, leukotriene and P2Y receptors utilize distinct membrane PIP2 pools. Our findings show that store-operated Ca2+ entry is needed to sustain cytoplasmic Ca2+ signaling following leukotriene receptor activation both by refilling the Ca2+ stores and by helping to replenish the PIP2 pool accessible to leukotriene receptors, ostensibly through control of PIP5 kinase activity.
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Affiliation(s)
- Abdullah Alswied
- From the Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Anant B Parekh
- From the Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
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24
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Samanta K, Kar P, Mirams GR, Parekh AB. Ca(2+) Channel Re-localization to Plasma-Membrane Microdomains Strengthens Activation of Ca(2+)-Dependent Nuclear Gene Expression. Cell Rep 2015; 12:203-16. [PMID: 26146085 PMCID: PMC4521080 DOI: 10.1016/j.celrep.2015.06.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 05/15/2015] [Accepted: 06/04/2015] [Indexed: 12/25/2022] Open
Abstract
In polarized cells or cells with complex geometry, clustering of plasma-membrane (PM) ion channels is an effective mechanism for eliciting spatially restricted signals. However, channel clustering is also seen in cells with relatively simple topology, suggesting it fulfills a more fundamental role in cell biology than simply orchestrating compartmentalized responses. Here, we have compared the ability of store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels confined to PM microdomains with a similar number of dispersed CRAC channels to activate transcription factors, which subsequently increase nuclear gene expression. For similar levels of channel activity, we find that channel confinement is considerably more effective in stimulating gene expression. Our results identify a long-range signaling advantage to the tight evolutionary conservation of channel clustering and reveal that CRAC channel aggregation increases the strength, fidelity, and reliability of the general process of excitation-transcription coupling.
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Affiliation(s)
- Krishna Samanta
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Pulak Kar
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Gary R Mirams
- Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
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25
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Samanta K, Douglas S, Parekh AB. Mitochondrial calcium uniporter MCU supports cytoplasmic Ca2+ oscillations, store-operated Ca2+ entry and Ca2+-dependent gene expression in response to receptor stimulation. PLoS One 2014; 9:e101188. [PMID: 25004162 PMCID: PMC4086884 DOI: 10.1371/journal.pone.0101188] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 06/04/2014] [Indexed: 12/21/2022] Open
Abstract
Ca2+ flux into mitochondria is an important regulator of cytoplasmic Ca2+ signals, energy production and cell death pathways. Ca2+ uptake can occur through the recently discovered mitochondrial uniporter channel (MCU) but whether the MCU is involved in shaping Ca2+ signals and downstream responses to physiological levels of receptor stimulation is unknown. Here, we show that modest stimulation of leukotriene receptors with the pro-inflammatory signal LTC4 evokes a series of cytoplasmic Ca2+ oscillations that are rapidly and faithfully propagated into mitochondrial matrix. Knockdown of MCU or mitochondrial depolarisation, to reduce the driving force for Ca2+ entry into the matrix, prevents the mitochondrial Ca2+ rise and accelerates run down of the oscillations. The loss of cytoplasmic Ca2+ oscillations appeared to be a consequence of enhanced Ca2+-dependent inactivation of InsP3 receptors, which arose from the loss of mitochondrial Ca2+ buffering. Ca2+ dependent gene expression in response to leukotriene receptor activation was suppressed following knockdown of the MCU. In addition to buffering Ca2+ release, mitochondria also sequestrated Ca2+ entry through store-operated Ca2+ channels and this too was prevented following loss of MCU. MCU is therefore an important regulator of physiological pulses of cytoplasmic Ca2+.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channels/genetics
- Calcium Channels/metabolism
- Calcium Signaling/physiology
- Cytoplasm/metabolism
- Gene Expression Regulation
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Ion Transport
- Leukemia, Basophilic, Acute/genetics
- Leukemia, Basophilic, Acute/metabolism
- Leukemia, Basophilic, Acute/pathology
- Membrane Potential, Mitochondrial
- Mitochondria/metabolism
- RNA, Messenger/genetics
- Rats
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction
- Tumor Cells, Cultured
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Affiliation(s)
- Krishna Samanta
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Sophie Douglas
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Anant B. Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- * E-mail:
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26
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Kar P, Samanta K, Kramer H, Morris O, Bakowski D, Parekh AB. Dynamic assembly of a membrane signaling complex enables selective activation of NFAT by Orai1. Curr Biol 2014; 24:1361-1368. [PMID: 24909327 PMCID: PMC4062936 DOI: 10.1016/j.cub.2014.04.046] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 04/04/2014] [Accepted: 04/23/2014] [Indexed: 12/12/2022]
Abstract
NFAT-dependent gene expression is essential for the development and function of the nervous, immune, and cardiovascular systems and kidney, bone, and skeletal muscle [1]. Most NFAT protein resides in the cytoplasm because of extensive phosphorylation, which masks a nuclear localization sequence. Dephosphorylation by the Ca2+-calmodulin-activated protein phosphatase calcineurin triggers NFAT migration into the nucleus [2, 3]. In some cell types, NFAT can be activated by Ca2+ nanodomains near open store-operated Orai1 and voltage-gated Ca2+ channels in the plasma membrane [4, 5]. How local Ca2+ near Orai1 is detected and whether other Orai channels utilize a similar mechanism remain unclear. Here, we report that the paralog Orai3 fails to activate NFAT. Orai1 is effective in activating gene expression via Ca2+ nanodomains because it participates in a membrane-delimited signaling complex that forms after store depletion and brings calcineurin, via the scaffolding protein AKAP79, to calmodulin tethered to Orai1. By contrast, Orai3 interacts less well with AKAP79 after store depletion, rendering it ineffective in activating NFAT. A channel chimera of Orai3 with the N terminus of Orai1 was able to couple local Ca2+ entry to NFAT activation, identifying the N-terminal domain of Orai1 as central to Ca2+ nanodomain-transcription coupling. The formation of a store-dependent signaling complex at the plasma membrane provides for selective activation of a fundamental downstream response by Orai1. Ca2+ store depletion leads to the formation of a plasmalemmal signaling complex AKAP79, with bound calcineurin and NFAT1, couples to the N terminus of Orai1 channels Ca2+ entry though the channels releases activated NFAT, leading to gene expression These results identify a mechanism for selective activation of a response by Orai1
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Affiliation(s)
- Pulak Kar
- Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK
| | - Krishna Samanta
- Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK
| | - Holger Kramer
- Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK
| | - Otto Morris
- Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK
| | - Daniel Bakowski
- Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK
| | - Anant B Parekh
- Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK.
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27
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Yeh YC, Tang MJ, Parekh AB. Caveolin-1 alters the pattern of cytoplasmic Ca2+ oscillations and Ca2+-dependent gene expression by enhancing leukotriene receptor desensitization. J Biol Chem 2014; 289:17843-53. [PMID: 24755228 PMCID: PMC4067216 DOI: 10.1074/jbc.m114.553453] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cytoplasmic Ca2+ oscillations constitute a widespread signaling mode and are often generated in response to stimulation of G protein-coupled receptors that activate phospholipase C. In mast cells, repetitive Ca2+ oscillations can be evoked by modest activation of cysteinyl leukotriene type I receptors by the physiological trigger, leukotriene C4. The Ca2+ oscillations arise from regenerative Ca2+ release from inositol 1,4,5-trisphosphate-sensitive stores followed by Ca2+ entry through store-operated Ca2+ channels, and the latter selectively activate the Ca2+-dependent transcription factor NFAT. The cysteinyl leukotriene type I receptors desensitize through negative feedback by protein kinase C, which terminates the oscillatory Ca2+ response. Here, we show that the scaffolding protein caveolin-1 has a profound effect on receptor-driven Ca2+ signals and downstream gene expression. Overexpression of caveolin-1 increased receptor-phospholipase C coupling, resulting in initially larger Ca2+ release transients of longer duration but which then ran down quickly. NFAT-activated gene expression, triggered in response to the Ca2+ signal, was also reduced by caveolin-1. Mutagenesis studies revealed that these effects required a functional scaffolding domain within caveolin-1. Mechanistically, the increase in Ca2+ release in the presence of caveolin-1 activated protein kinase C, which accelerated homologous desensitization of the leukotriene receptor and thereby terminated the oscillatory Ca2+ response. Our results reveal that caveolin-1 is a bimodal regulator of receptor-dependent Ca2+ signaling, which fine-tunes the spatial and temporal profile of the Ca2+ rise and thereby its ability to activate the NFAT pathway.
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Affiliation(s)
- Yi-Chun Yeh
- From the Department of Physiology, Anatomy, and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, United Kingdom and
| | - Ming-Jer Tang
- the Department of Physiology, National Cheng Kung University Medical College, Tainan and Department of Life Science, Tunghai University, Taichung 40704, Taiwan
| | - Anant B Parekh
- From the Department of Physiology, Anatomy, and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, United Kingdom and
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28
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Parekh AB. An introduction to the Bioscience Birthday Symposium held in honour of Ole Petersen CBE, FRS. J Physiol 2014; 592:259-60. [DOI: 10.1113/jphysiol.2013.266429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Anant B. Parekh
- Department of Physiology, Anatomy and Genetics; Sherrington Building, Parks Road Oxford OX1 3PT UK
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29
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Bakowski D, Nelson C, Parekh AB. Endoplasmic reticulum-mitochondria coupling: local Ca²⁺ signalling with functional consequences. Pflugers Arch 2012; 464:27-32. [PMID: 22415215 DOI: 10.1007/s00424-012-1095-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 02/20/2012] [Accepted: 03/01/2012] [Indexed: 12/12/2022]
Abstract
Plasma membrane store-operated Ca²⁺ release-activated Ca²⁺ (CRAC) channels are a widespread and conserved Ca²⁺ influx pathway, driving activation of a range of spatially and temporally distinct cellular responses. Although CRAC channels are activated by the loss of Ca²⁺ from the endoplasmic reticulum, their gating is regulated by mitochondria. Through their ability to buffer cytoplasmic Ca²⁺, mitochondria take up Ca²⁺ released from the endoplasmic reticulum by InsP₃ receptors, leading to more extensive store depletion and stronger activation of CRAC channels. Mitochondria also buffer Ca²⁺ that enters through CRAC channels, reducing Ca²⁺-dependent slow inactivation of the channels. In addition, depolarised mitochondria impair movement of the CRAC channel activating protein STIM1 across the endoplasmic reticulum membrane. Because they regulate CRAC channel activity, particularly Ca²⁺-dependent slow inactivation, mitochondria influence CRAC channel-driven enzyme activation, secretion and gene expression. Mitochondrial regulation of CRAC channels therefore provides an important control element to the regulation of intracellular Ca²⁺ signalling.
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Affiliation(s)
- Daniel Bakowski
- Department of Physiology, Anatomy and Genetics Sherrington Building, South Parks Road, Oxford, OX1 3PT, UK
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30
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Trebak M, Parekh AB. Ion channels in patho-physiology. J Physiol 2012; 590:1347. [DOI: 10.1113/jphysiol.2012.230219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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31
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Kar P, Nelson C, Parekh AB. CRAC channels drive digital activation and provide analog control and synergy to Ca(2+)-dependent gene regulation. Curr Biol 2012; 22:242-7. [PMID: 22245003 DOI: 10.1016/j.cub.2011.12.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 11/18/2011] [Accepted: 12/09/2011] [Indexed: 01/18/2023]
Abstract
Ca(2+)-dependent gene expression is critical for cell growth, proliferation, plasticity, and adaptation [1-3]. Because a common mechanism in vertebrates linking cytoplasmic Ca(2+) signals with activation of protein synthesis involves the nuclear factor of activated T cells (NFAT) family of transcription factors [4, 5], we have quantified protein expression in single cells following physiological Ca(2+) signals by using NFAT-driven expression of a genetically encoded fluorescent protein. We find that gene expression following CRAC channel activation is an all-or-nothing event over a range of stimulus intensities. Increasing agonist concentration recruits more cells but each responding cell does so in an essentially digital manner. Furthermore, Ca(2+)-dependent gene expression shows both short-term memory and strong synergy, where two pulses of agonist, which are ineffectual individually, robustly activate gene expression provided that the time interval between them is short. Such temporal filtering imparts coincidence detection to Ca(2+)-dependent gene activation. The underlying molecular basis mapped to time-dependent, nonlinear accumulation of nuclear NFAT. Local Ca(2+) near CRAC channels has to rise above a threshold level to drive gene expression, providing analog control to the digital activation process and a means to filter out fluctuations in background noise from activating transcription while ensuring robustness and high fidelity in the excitation-transcription coupling mechanism.
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Affiliation(s)
- Pulak Kar
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
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32
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Parekh AB. Alison F. Brading (1939-2011). J Physiol 2011. [DOI: 10.1113/jphysiol.2011.207589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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34
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Kar P, Nelson C, Parekh AB. Selective activation of the transcription factor NFAT1 by calcium microdomains near Ca2+ release-activated Ca2+ (CRAC) channels. J Biol Chem 2011; 286:14795-803. [PMID: 21325277 DOI: 10.1074/jbc.m111.220582] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
NFATs are a family of Ca(2+)-dependent transcription factors that play a central role in the morphogenesis, development, and physiological activities of numerous distinct cell types and organ systems. Here, we visualize NFAT1 movement in and out of the nucleus in response to transient activation of store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels in nonexcitable cells. We show that NFAT migration is exquisitely sensitive to Ca(2+) microdomains near open CRAC channels. Another Ca(2+)-permeable ion channel (TRPC3) was ineffective in driving NFAT1 to the nucleus. NFAT1 movement is temporally dissociated from the time course of the Ca(2+) signal and remains within the nucleus for 10 times longer than the duration of the trigger Ca(2+) signal. Kinetic analyses of each step linking CRAC channel activation to NFAT1 nuclear residency reveals that the rate-limiting step is transcription factor exit from the nucleus. The slow deactivation of NFAT provides a mechanism whereby Ca(2+)-dependent responses can be sustained despite the termination of the initial Ca(2+) signal and helps explain how gene expression in nonexcitable cells can continue after the primary stimulus has been removed.
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Affiliation(s)
- Pulak Kar
- Department of Physiology, Oxford University, Sherrington Building, Parks Road, Oxford OX1 3PT, United Kingdom
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Singaravelu K, Nelson C, Bakowski D, de Brito OM, Ng SW, Di Capite J, Powell T, Scorrano L, Parekh AB. Mitofusin 2 regulates STIM1 migration from the Ca2+ store to the plasma membrane in cells with depolarized mitochondria. J Biol Chem 2011; 286:12189-201. [PMID: 21220420 DOI: 10.1074/jbc.m110.174029] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Store-operated Ca2+ channels in the plasma membrane (PM) are activated by the depletion of Ca2+ from the endoplasmic reticulum (ER) and constitute a widespread and highly conserved Ca2+ influx pathway. After store emptying, the ER Ca2+ sensor STIM1 forms multimers, which then migrate to ER-PM junctions where they activate the Ca2+ release-activated Ca2+ channel Orai1. Movement of an intracellular protein to such specialized sites where it gates an ion channel is without precedence, but the fundamental question of how STIM1 migrates remains unresolved. Here, we show that trafficking of STIM1 to ER-PM junctions and subsequent Ca2+ release-activated Ca2+ channel activity is impaired following mitochondrial depolarization. We identify the dynamin-related mitochondrial protein mitofusin 2, mutations of which causes the inherited neurodegenerative disease Charcot-Marie-Tooth IIa in humans, as an important component of this mechanism. Our results reveal a molecular mechanism whereby a mitochondrial fusion protein regulates protein trafficking across the endoplasmic reticulum and reveals a homeostatic mechanism whereby mitochondrial depolarization can inhibit store-operated Ca2+ entry, thereby reducing cellular Ca2+ overload.
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Affiliation(s)
- Karthika Singaravelu
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, United Kingdom
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36
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Abstract
A rise in cytosolic Ca(2+) concentration is used as a universal signalling mechanism to control biological processes as diverse as exocytosis, contraction, cell growth and cell death. Ca(2+) signals are often presented to cells in the form of Ca(2+) oscillations, with signalling information encoded in both amplitude and frequency of the Ca(2+) spikes. Recent studies have revealed that the sub-cellular spatial profile of the Ca(2+) oscillation is also important in activating cellular responses, thereby suggesting a new mechanism for extracting information from the ubiquitous Ca(2+) oscillation.
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Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Sherrington Building, Parks Road, Oxford OX1 3PT, UK.
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37
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Abstract
Elevation of cytosolic Ca(2+) levels through the activation of store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels is involved in mediating a disparate array of cellular responses. These include secretion, metabolism and gene expression, as well as cell growth and proliferation. Moreover, emerging evidence points to the involvement of aberrant CRAC channel activity in human diseases, such as certain types of immunodeficiency and autoimmunity disorders, allergy, and inflammatory bowel disease. This article summarizes recent advances in understanding the gating and function of CRAC channels, their links to human disease and key issues for the development of channel blockers.
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Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
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Di Capite J, Nelson C, Bates G, Parekh AB. Targeting Ca2+ release-activated Ca2+ channel channels and leukotriene receptors provides a novel combination strategy for treating nasal polyposis. J Allergy Clin Immunol 2009; 124:1014-21.e1-3. [PMID: 19895990 DOI: 10.1016/j.jaci.2009.08.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 07/16/2009] [Accepted: 08/03/2009] [Indexed: 11/24/2022]
Abstract
BACKGROUND Nasal polyposis is a chronic inflammatory disease of the upper respiratory tract that affects around 2% of the population and almost 67% of patients with aspirin-intolerant asthma. Polyps are rich in mast cells and eosinophils, resulting in high levels of the proinflammatory cysteinyl leukotrienes. OBJECTIVES To better understand the role of the proinflammatory leukotrienes in nasal polyposis, we asked the following questions: (1) How do nasal polyps produce leukotriene C(4) (LTC(4))? (2) Can LTC(4) feed back in a paracrine way to maintain mast cell activation? (3) Could a combination therapy targeting the elements of this feed-forward loop provide a novel therapy for allergic disease? METHODS We have used immunohistochemistry, enzyme immunoassay, and cytoplasmic calcium ion (Ca(2+)) imaging to address these questions on cultured and acutely isolated human mast cells from patients with polyposis. RESULTS Ca(2+) entry through store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels in polyps produced LTC(4) in a manner dependent on protein kinase C. LTC(4) thus generated activated mast cells through cysteinyl leukotriene type I receptors. Hence Ca(2+) influx into mast cells stimulates LTC(4) production, which then acts as a paracrine signal to activate further Ca(2+) influx. A combination of a low concentration of both a CRAC channel blocker and a leukotriene receptor antagonist was as effective at suppressing mast cell activation as a high concentration of either antagonist alone. CONCLUSION A drug combination directed against CRAC channels and leukotriene receptor antagonist suppresses the feed-forward loop that leads to aberrant mast cell activation. Hence our results identify a new potential strategy for combating polyposis and mast cell-dependent allergies.
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Affiliation(s)
- Joseph Di Capite
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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Ng SW, Nelson C, Parekh AB. Coupling of Ca(2+) microdomains to spatially and temporally distinct cellular responses by the tyrosine kinase Syk. J Biol Chem 2009; 284:24767-72. [PMID: 19584058 DOI: 10.1074/jbc.m109.011692] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Communication between the cell surface and the nucleus is essential for regulated gene expression. In neurons, Ca(2+)-dependent gene transcription is sensitive to local Ca(2+) entry. In immune cells, excitation-transcription coupling is thought to involve global Ca(2+) signals. Here, we show that in mast cells, Ca(2+) microdomains from store-operated Ca(2+) release-activated Ca(2+) channels activate expression of the transcription factor c-fos. Local Ca(2+) entry is sensed by the tyrosine kinase Syk, which signals to the nucleus through the transcription factor STAT5. Ca(2+) microdomains also promote secretion of proinflammatory messengers, which, like gene expression, requires Syk. Syk therefore couples Ca(2+) microdomains to the activation of two spatially and temporally distinct cellular responses, revealing the versatility of local Ca(2+) signals in driving cell activation.
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Affiliation(s)
- Siaw-Wei Ng
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, United Kingdom
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Di Capite J, Ng SW, Parekh AB. Decoding of cytoplasmic Ca(2+) oscillations through the spatial signature drives gene expression. Curr Biol 2009; 19:853-8. [PMID: 19375314 DOI: 10.1016/j.cub.2009.03.063] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Revised: 03/19/2009] [Accepted: 03/19/2009] [Indexed: 11/15/2022]
Abstract
Cytoplasmic Ca(2+) oscillations are a universal signaling mode that activates numerous cellular responses [1, 2]. Oscillations are considered the physiological mechanism of Ca(2+) signaling because they occur at low levels of stimulus intensity [3]. Ca(2+) oscillations are proposed to convey information in their amplitude and frequency, leading to activation of specific downstream targets [4-6]. Here, we report that the spatial Ca(2+) gradient within the oscillation is key. Ca(2+) oscillations in mast cells evoked over a range of agonist concentrations in the presence of external Ca(2+) were indistinguishable from those in the absence of Ca(2+) when plasmalemmal Ca(2+) extrusion was suppressed. Nevertheless, only oscillations with accompanying Ca(2+) entry through store-operated CRAC channels triggered gene expression. Increased cytoplasmic Ca(2+) buffering prevented oscillations but not gene activation. Local Ca(2+) influx and not global Ca(2+) oscillations therefore drives gene expression at physiological levels of stimulation. Rather than serving to maintain Ca(2+) oscillations by replenishing stores, we suggest that the role of oscillations might be to activate CRAC channels, thereby ensuring the generation of spatially restricted physiological Ca(2+) signals driving gene activation. Furthermore, we show that the spatial profile of a Ca(2+) oscillation provides a novel mechanism whereby a pleiotropic messenger specifically activates gene expression.
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Affiliation(s)
- Joseph Di Capite
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
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42
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Abstract
Ca(2+) entry through store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels controls a disparate array of key cellular responses. In this review, recent work will be described that shows local Ca(2+) influx through CRAC channels has important spatial and temporal consequences on cell function. A localized Ca(2+) rise below the plasma membrane activates, within tens of seconds, catabolic enzymes resulting in the generation of the intracellular messenger arachidonic acid and the paracrine pro-inflammatory molecule LTC(4). In addition, local Ca(2+) entry can activate gene expression, which develops over tens of minutes. Local Ca(2+) influx through CRAC channels therefore has far-reaching consequences on intra- and intercellular communication.
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Affiliation(s)
- A B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, UK.
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Di Capite J, Shirley A, Nelson C, Bates G, Parekh AB. Intercellular Ca2+ wave propagation involving positive feedback between CRAC channels and cysteinyl leukotrienes. FASEB J 2008; 23:894-905. [PMID: 18978154 DOI: 10.1096/fj.08-118935] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mast cells are key components of the immune system, where they help orchestrate the inflammatory response. Aberrant mast cell activation is linked to a variety of allergic diseases, including asthma, eczema, rhinitis, and nasal polyposis, which in combination affect up to 20% of the population in industrialized countries. On activation, mast cells release a variety of signals that target the bronchi and vasculature and recruit other immune cells to the inflammatory site. Prominent among such signals are the cysteinyl leukotrienes, a family of potent proinflammatory lipid mediators comprising leukotriene C(4) (LTC(4)), LTD(4), and LTE(4). LTC(4), the parent compound, is secreted from mast cells following Ca(2+) influx through store-operated calcium release-activated calcium (CRAC) channels. Here, we show that activated mast cells release a paracrine signal that evokes Ca(2+) signals in spatially separate resting mast cells. The paracrine signal was identified as a cysteinyl leukotriene because 1) RNAi knockdown or pharmacological block of the 5-lipoxygenase enzyme prevented activated mast cells from stimulating resting cells. 2) Block of cysteinyl leukotriene type I receptors on resting mast cells with the clinically prescribed receptor antagonist montelukast prevented their activation by active mast cells. 3) RNAi knockdown of cysteinyl leukotriene type I receptors on resting cells prevented them from responding to the paracrine signal derived from activated mast cells. 4) Purified LTC(4) evoked Ca(2+) signals in mast cells that were identical to those triggered by the paracrine signal. Low levels of stimulus intensity released sufficient levels of leukotriene to activate resting cells. Leukotriene secretion still occurred tens of minutes after stimulation, suggesting a role as a long-lasting trigger in mast cell activation. Stimulation of the cysteinyl leukotriene receptor activated CRAC channels and evoked prominent store-operated Ca(2+) entry. This resulted in further cysteinyl leukotriene production, triggering a positive feedback cascade. Acutely isolated mast cells from patients with allergic rhinitis exhibited store-operated Ca(2+) influx through CRAC channels and responded to cysteinyl leukotrienes. Histological analysis of samples taken from patients revealed clustering of mast cells, often located within 20 microm of each other, a distance sufficient for paracrine signaling by leukotrienes to operate effectively. We conclude that a positive-feedback cascade involving CRAC channels and cysteinyl leukotrienes constitute a novel mechanism for sustaining mast cell activation.
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Affiliation(s)
- Joseph Di Capite
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
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45
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Ng SW, di Capite J, Singaravelu K, Parekh AB. Sustained activation of the tyrosine kinase Syk by antigen in mast cells requires local Ca2+ influx through Ca2+ release-activated Ca2+ channels. J Biol Chem 2008; 283:31348-55. [PMID: 18806259 DOI: 10.1074/jbc.m804942200] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mast cell activation involves cross-linking of IgE receptors followed by phosphorylation of the non-receptor tyrosine kinase Syk. This results in activation of the plasma membrane-bound enzyme phospholipase Cgamma1, which hydrolyzes the minor membrane phospholipid phosphatidylinositol 4,5-bisphosphate to generate diacylglycerol and inositol trisphosphate. Inositol trisphosphate raises cytoplasmic Ca2+ concentration by releasing Ca2+ from intracellular stores. This Ca2+ release phase is accompanied by sustained Ca2+ influx through store-operated Ca2+ release-activated Ca2+ (CRAC) channels. Here, we find that engagement of IgE receptors activates Syk, and this leads to Ca2+ release from stores followed by Ca2+ influx. The Ca2+ influx phase then sustains Syk activity. The Ca2+ influx pathway activated by these receptors was identified as the CRAC channel, because pharmacological block of the channels with either a low concentration of Gd3+ or exposure to the novel CRAC channel blocker 3-fluoropyridine-4-carboxylic acid (2',5'-dimethoxybiphenyl-4-yl)amide or RNA interference knockdown of Orai1, which encodes the CRAC channel pore, all prevented the increase in Syk activity triggered by Ca2+ entry. CRAC channels and Syk are spatially close together, because increasing cytoplasmic Ca2+ buffering with the fast Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis failed to prevent activation of Syk by Ca2+ entry. Our results reveal a positive feedback step in mast cell activation where receptor-triggered Syk activation and subsequent Ca2+ release opens CRAC channels, and the ensuing local Ca2+ entry then maintains Syk activity. Ca2+ entry through CRAC channels therefore provides a means whereby the Ca2+ and tyrosine kinase signaling pathways can interact with one another.
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Affiliation(s)
- Siaw Wei Ng
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Sherrington Bldg., Parks Road, Oxford OX1 3PT, United Kingdom
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46
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Moreau B, Parekh AB. Ca2+ -dependent inactivation of the mitochondrial Ca2+ uniporter involves proton flux through the ATP synthase. Curr Biol 2008; 18:855-9. [PMID: 18514515 DOI: 10.1016/j.cub.2008.05.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Revised: 05/07/2008] [Accepted: 05/07/2008] [Indexed: 10/22/2022]
Abstract
Stimulation of receptors on the surface of animal cells often evokes cellular responses by raising intracellular Ca(2+) concentration. The rise in cytoplasmic Ca(2+) drives a plethora of processes, including neurotransmitter release, muscle contraction, and cell growth and proliferation. Mitochondria help shape intracellular Ca(2+) signals through their ability to rapidly take up significant amounts of Ca(2+) from the cytosol via the uniporter, a Ca(2+)-selective ion channel in the inner mitochondrial membrane. The uniporter is subject to inactivation, whereby a sustained cytoplasmic Ca(2+) rise prevents further Ca(2+) uptake. In spite of its importance in intracellular Ca(2+) signaling, little is known about the mechanism underlying uniporter inactivation. Here, we report that maneuvers that promote matrix alkalinisation significantly reduce inactivation whereas acidification exacerbates it. We further show that the F(1)F(0)-ATP synthase complex is an important source of protons for inactivation of the uniporter. These findings identify a novel molecular mechanism that regulates the activity of this ubiquitous intracellular Ca(2+) channel, with implications for intracellular Ca(2+) signaling and aerobic ATP production.
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Affiliation(s)
- Ben Moreau
- Department of Physiology, Anatomy and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK
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47
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Abstract
In eukaryotic cells, a rise in cytoplasmic Ca(2+) can activate a plethora of responses that operate on time scales ranging from milliseconds to days. Inherent to the use of a promiscuous signal like Ca(2+) is the problem of specificity: how can Ca(2+) activate some responses but not others? We now know that the spatial profile of the Ca(2+) signal is important Ca(2+) does not simply rise uniformly throughout the cytoplasm upon stimulation but can reach very high levels locally, creating spatial gradients. The most fundamental local Ca(2+) signal is the Ca(2+) microdomain that develops rapidly near open plasmalemmal Ca(2+) channels like voltage-gated L-type (Cav1.2) and store-operated CRAC channels. Recent work has revealed that Ca(2+) microdomains arising from these channels are remarkably versatile in triggering a range of responses that differ enormously in both temporal and spatial profile. Here, I delineate basic features of Ca(2+) microdomains and then describe how these highly local signals are used by Ca(2+)-permeable channels to drive cellular responses.
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Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK.
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48
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Abstract
In eukaryotic cells, one major route for Ca(2+) influx is through store-operated CRAC channels, which are activated following a fall in Ca(2+) content within the endoplasmic reticulum. Mitochondria are key regulators of this ubiquitous Ca(2+) influx pathway. Respiring mitochondria rapidly take up some of the Ca(2+) released from the stores, resulting in more extensive store depletion and thus robust activation of CRAC channels. As CRAC channels open, the ensuing rise in cytoplasmic Ca(2+) feeds back to inactivate the channels. By buffering some of the incoming Ca(2+) mitochondria reduce Ca(2+)-dependent inactivation of the CRAC channels, resulting in more prolonged Ca(2+) influx. However, mitochondria can release Ca(2+) close to the endoplasmic reticulum, accelerating store refilling and thus promoting deactivation of the CRAC channels. Mitochondria thus regulate all major transitions in CRAC channel gating, revealing remarkable versatility in how this organelle impacts upon Ca(2+) influx. Recent evidence suggests that mitochondria also control CRAC channels through mechanisms that are independent of their Ca(2+)-buffering actions and ability to generate ATP. Furthermore, pyruvic acid, a key intermediary metabolite and precursor substrate for the Krebs cycle, reduces the extent of Ca(2+)-dependent inactivation of CRAC channels. Hence mitochondrial metabolism impacts upon Ca(2+) influx through CRAC channels and thus on a range of key downstream cellular responses.
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Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, UK.
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Chang WC, Di Capite J, Singaravelu K, Nelson C, Halse V, Parekh AB. Local Ca2+ influx through Ca2+ release-activated Ca2+ (CRAC) channels stimulates production of an intracellular messenger and an intercellular pro-inflammatory signal. J Biol Chem 2007; 283:4622-31. [PMID: 18156181 DOI: 10.1074/jbc.m705002200] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca2+ entry through store-operated Ca2+ channels drives the production of the pro-inflammatory molecule leukotriene C4 (LTC4) from mast cells through a pathway involving Ca2+-dependent protein kinase C, mitogen-activated protein kinases ERK1/2, phospholipase A2, and 5-lipoxygenase. Here we examine whether local Ca2+ influx through store-operated Ca2+ release-activated Ca2+ (CRAC) channels in the plasma membrane stimulates this signaling pathway. Manipulating the amplitude and spatial extent of Ca2+ entry by altering chemical and electrical gradients for Ca2+ influx or changing the Ca2+ buffering of the cytoplasm all impacted on protein kinase C and ERK activation, generation of arachidonic acid and LTC4 secretion, with little change in the bulk cytoplasmic Ca2+ rise. Similar bulk cytoplasmic Ca2+ concentrations were achieved when CRAC channels were activated in 0.25 mm external Ca2+ versus 2 mm Ca2+ and 100 nm La3+, an inhibitor of CRAC channels. However, despite similar bulk cytoplasmic Ca2+, protein kinase C activation and LTC4 secretion were larger in 2 mm Ca2+ and La3+ than in 0.25 mm Ca2+, consistent with the central involvement of a subplasmalemmal Ca2+ rise. The nonreceptor tyrosine kinase Syk coupled CRAC channel opening to protein kinase C and ERK activation. Recombinant TRPC3 channels also activated protein kinase C, suggesting that subplasmalemmal Ca2+ rather than a microdomain exclusive to CRAC channels is the trigger. Hence a subplasmalemmal Ca2+ increase in mast cells is highly versatile in that it triggers cytoplasmic responses through generation of intracellular messengers as well as long distance changes through increased secretion of paracrine signals.
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Affiliation(s)
- Wei-Chiao Chang
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Parks Road, Oxford OX1 3PT, United Kingdom
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Chang WC, Di Capite J, Nelson C, Parekh AB. All-or-none activation of CRAC channels by agonist elicits graded responses in populations of mast cells. J Immunol 2007; 179:5255-63. [PMID: 17911611 DOI: 10.4049/jimmunol.179.8.5255] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In nonexcitable cells, receptor stimulation evokes Ca(2+) release from the endoplasmic reticulum stores followed by Ca(2+) influx through store-operated Ca(2+) channels in the plasma membrane. In mast cells, store-operated entry is mediated via Ca(2+) release-activated Ca(2+) (CRAC) channels. In this study, we find that stimulation of muscarinic receptors in cultured mast cells results in Ca(2+)-dependent activation of protein kinase Calpha and the mitogen activated protein kinases ERK1/2 and this is required for the subsequent stimulation of the enzymes Ca(2+)-dependent phospholipase A(2) and 5-lipoxygenase, generating the intracellular messenger arachidonic acid and the proinflammatory intercellular messenger leukotriene C(4). In cell population studies, ERK activation, arachidonic acid release, and leukotriene C(4) secretion were all graded with stimulus intensity. However, at a single cell level, Ca(2+) influx was related to agonist concentration in an essentially all-or-none manner. This paradox of all-or-none CRAC channel activation in single cells with graded responses in cell populations was resolved by the finding that increasing agonist concentration recruited more mast cells but each cell responded by generating all-or-none Ca(2+) influx. These findings were extended to acutely isolated rat peritoneal mast cells where muscarinic or P2Y receptor stimulation evoked all-or-none activation of Ca(2+)entry but graded responses in cell populations. Our results identify a novel way for grading responses to agonists in immune cells and highlight the importance of CRAC channels as a key pharmacological target to control mast cell activation.
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Affiliation(s)
- Wei-Chiao Chang
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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