1
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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] [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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2
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Barak P, Kaur S, Scappini E, Tucker CJ, Parekh AB. Plasma Membrane Ca 2+ ATPase Activity Enables Sustained Store-operated Ca 2+ Entry in the Absence of a Bulk Cytosolic Ca 2+ Rise. FUNCTION 2022; 3:zqac040. [PMID: 38989036 PMCID: PMC11234650 DOI: 10.1093/function/zqac040] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/11/2022] [Accepted: 08/12/2022] [Indexed: 07/12/2024] Open
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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3
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Kim JH, Carreras-Sureda A, Didier M, Henry C, Frieden M, Demaurex N. The TAM-associated STIM1I484R mutation increases ORAI1 channel function due to a reduced STIM1 inactivation break and an absence of microtubule trapping. Cell Calcium 2022; 105:102615. [DOI: 10.1016/j.ceca.2022.102615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 06/15/2022] [Accepted: 06/16/2022] [Indexed: 11/26/2022]
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Regulation of Store-Operated Ca 2+ Entry by SARAF. Cells 2021; 10:cells10081887. [PMID: 34440656 PMCID: PMC8391525 DOI: 10.3390/cells10081887] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/19/2021] [Accepted: 07/22/2021] [Indexed: 12/14/2022] Open
Abstract
Calcium (Ca2+) signaling plays a dichotomous role in cellular biology, controlling cell survival and proliferation on the one hand and cellular toxicity and cell death on the other. Store-operated Ca2+ entry (SOCE) by CRAC channels represents a major pathway for Ca2+ entry in non-excitable cells. The CRAC channel has two key components, the endoplasmic reticulum Ca2+ sensor stromal interaction molecule (STIM) and the plasma-membrane Ca2+ channel Orai. Physical coupling between STIM and Orai opens the CRAC channel and the resulting Ca2+ flux is regulated by a negative feedback mechanism of slow Ca2+ dependent inactivation (SCDI). The identification of the SOCE-associated regulatory factor (SARAF) and investigations of its role in SCDI have led to new functional and molecular insights into how SOCE is controlled. In this review, we provide an overview of the functional and molecular mechanisms underlying SCDI and discuss how the interaction between SARAF, STIM1, and Orai1 shapes Ca2+ signaling in cells.
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Cross-Talk Between the Adenylyl Cyclase/cAMP Pathway and Ca 2+ Homeostasis. Rev Physiol Biochem Pharmacol 2021; 179:73-116. [PMID: 33398503 DOI: 10.1007/112_2020_55] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cyclic AMP and Ca2+ are the first second or intracellular messengers identified, unveiling the cellular mechanisms activated by a plethora of extracellular signals, including hormones. Cyclic AMP generation is catalyzed by adenylyl cyclases (ACs), which convert ATP into cAMP and pyrophosphate. By the way, Ca2+, as energy, can neither be created nor be destroyed; Ca2+ can only be transported, from one compartment to another, or chelated by a variety of Ca2+-binding molecules. The fine regulation of cytosolic concentrations of cAMP and free Ca2+ is crucial in cell function and there is an intimate cross-talk between both messengers to fine-tune the cellular responses. Cancer is a multifactorial disease resulting from a combination of genetic and environmental factors. Frequent cases of cAMP and/or Ca2+ homeostasis remodeling have been described in cancer cells. In those tumoral cells, cAMP and Ca2+ signaling plays a crucial role in the development of hallmarks of cancer, including enhanced proliferation and migration, invasion, apoptosis resistance, or angiogenesis. This review summarizes the cross-talk between the ACs/cAMP and Ca2+ intracellular pathways with special attention to the functional and reciprocal regulation between Orai1 and AC8 in normal and cancer cells.
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6
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Liu G, Fu D, Tian H, Dai A. The mechanism of ions in pulmonary hypertension. Pulm Circ 2021; 11:2045894020987948. [PMID: 33614016 PMCID: PMC7869166 DOI: 10.1177/2045894020987948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 12/23/2020] [Indexed: 12/15/2022] Open
Abstract
Pulmonary hypertension(PH)is a kind of hemodynamic and pathophysiological state, in which the pulmonary artery pressure (PAP) rises above a certain threshold. The main pathological manifestation is pulmonary vasoconstriction and remodelling progressively. More and more studies have found that ions play a major role in the pathogenesis of PH. Many vasoactive substances, inflammatory mediators, transcription-inducing factors, apoptosis mediators, redox substances and translation modifiers can control the concentration of ions inside and outside the cell by regulating the activity of ion channels, which can regulate vascular contraction, cell proliferation, migration, apoptosis, inflammation and other functions. We all know that there are no effective drugs to treat PH. Ions are involved in the occurrence and development of PH, so it is necessary to clarify the mechanism of ions in PH as a therapeutic target for PH. The main ions involved in PH are calcium ion (Ca2+), potassium ion (K+), sodium ion (Na+) and chloride ion (Cl-). Here, we mainly discuss the distribution of these ions and their channels in pulmonary arteries and their role in the pathogenesis of PH.
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Affiliation(s)
- Guogu Liu
- Department of Graduate School, University of South China,
Hengyang, China
- Department of Respiratory Medicine, Hunan Provincial People’s
Hospital, Changsha, China
| | - Daiyan Fu
- Department of Respiratory Medicine, Hunan Provincial People’s
Hospital, Changsha, China
| | - Heshen Tian
- Department of Graduate School, University of South China,
Hengyang, China
- Department of Respiratory Medicine, Hunan Provincial People’s
Hospital, Changsha, China
| | - Aiguo Dai
- Department of Respiratory Diseases, Hunan University of Chinese
Medicine, Changsha, China
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7
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Cytosolic and intra-organellar Ca2+ oscillations: mechanisms and function. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Bakowski D, Murray F, Parekh AB. Store-Operated Ca 2+ Channels: Mechanism, Function, Pharmacology, and Therapeutic Targets. Annu Rev Pharmacol Toxicol 2020; 61:629-654. [PMID: 32966177 DOI: 10.1146/annurev-pharmtox-031620-105135] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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9
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Silva BSC, DiGiovanni L, Kumar R, Carmichael RE, Kim PK, Schrader M. Maintaining social contacts: The physiological relevance of organelle interactions. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118800. [PMID: 32712071 PMCID: PMC7377706 DOI: 10.1016/j.bbamcr.2020.118800] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/12/2020] [Accepted: 07/19/2020] [Indexed: 02/07/2023]
Abstract
Membrane-bound organelles in eukaryotic cells form an interactive network to coordinate and facilitate cellular functions. The formation of close contacts, termed "membrane contact sites" (MCSs), represents an intriguing strategy for organelle interaction and coordinated interplay. Emerging research is rapidly revealing new details of MCSs. They represent ubiquitous and diverse structures, which are important for many aspects of cell physiology and homeostasis. Here, we provide a comprehensive overview of the physiological relevance of organelle contacts. We focus on mitochondria, peroxisomes, the Golgi complex and the plasma membrane, and discuss the most recent findings on their interactions with other subcellular organelles and their multiple functions, including membrane contacts with the ER, lipid droplets and the endosomal/lysosomal compartment.
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Affiliation(s)
- Beatriz S C Silva
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter EX4 4QD, Devon, UK
| | - Laura DiGiovanni
- Program in Cell Biology, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Rechal Kumar
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter EX4 4QD, Devon, UK
| | - Ruth E Carmichael
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter EX4 4QD, Devon, UK.
| | - Peter K Kim
- Program in Cell Biology, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada.
| | - Michael Schrader
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter EX4 4QD, Devon, UK.
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10
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Lopez JJ, Jardin I, Albarrán L, Sanchez-Collado J, Cantonero C, Salido GM, Smani T, Rosado JA. Molecular Basis and Regulation of Store-Operated Calcium Entry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:445-469. [PMID: 31646520 DOI: 10.1007/978-3-030-12457-1_17] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Store-operated Ca2+ entry (SOCE) is a ubiquitous mechanism for Ca2+ influx in mammalian cells with important physiological implications. Since the discovery of SOCE more than three decades ago, the mechanism that communicates the information about the amount of Ca2+ accumulated in the intracellular Ca2+ stores to the plasma membrane channels and the nature of these channels have been matters of intense investigation and debate. The stromal interaction molecule-1 (STIM1) has been identified as the Ca2+ sensor of the intracellular Ca2+ compartments that activates the store-operated channels. STIM1 regulates two types of store-dependent channels: the Ca2+ release-activated Ca2+ (CRAC) channels, formed by Orai1 subunits, that conduct the highly Ca2+ selective current I CRAC and the cation permeable store-operated Ca2+ (SOC) channels, which consist of Orai1 and TRPC1 proteins and conduct the non-selective current I SOC. While the crystal structure of Drosophila CRAC channel has already been solved, the architecture of the SOC channels still remains unclear. The dynamic interaction of STIM1 with the store-operated channels is modulated by a number of proteins that either support the formation of the functional STIM1-channel complex or protect the cell against Ca2+ overload.
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Affiliation(s)
- Jose J Lopez
- Department of Physiology, Cell Physiology Research Group and Institute of Molecular Pathology Biomarkers, University of Extremadura, Cáceres, Spain
| | - Isaac Jardin
- Department of Physiology, Cell Physiology Research Group and Institute of Molecular Pathology Biomarkers, University of Extremadura, Cáceres, Spain.
| | - Letizia Albarrán
- Department of Physiology, Cell Physiology Research Group and Institute of Molecular Pathology Biomarkers, University of Extremadura, Cáceres, Spain
| | - Jose Sanchez-Collado
- Department of Physiology, Cell Physiology Research Group and Institute of Molecular Pathology Biomarkers, University of Extremadura, Cáceres, Spain
| | - Carlos Cantonero
- Department of Physiology, Cell Physiology Research Group and Institute of Molecular Pathology Biomarkers, University of Extremadura, Cáceres, Spain
| | - Gines M Salido
- Department of Physiology, Cell Physiology Research Group and Institute of Molecular Pathology Biomarkers, University of Extremadura, Cáceres, Spain
| | - Tarik Smani
- Department of Medical Physiology and Biophysics and Group of Cardiovascular Pathophysiology, Institute of Biomedicine of Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/University of Sevilla, Sevilla, Spain
| | - Juan A Rosado
- Department of Physiology, Cell Physiology Research Group and Institute of Molecular Pathology Biomarkers, University of Extremadura, Cáceres, Spain
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11
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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] [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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12
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Bulla M, Gyimesi G, Kim JH, Bhardwaj R, Hediger MA, Frieden M, Demaurex N. ORAI1 channel gating and selectivity is differentially altered by natural mutations in the first or third transmembrane domain. J Physiol 2018; 597:561-582. [PMID: 30382595 PMCID: PMC6332830 DOI: 10.1113/jp277079] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 10/31/2018] [Indexed: 12/12/2022] Open
Abstract
KEY POINTS Gain-of-function mutations in the highly selective Ca2+ channel ORAI1 cause tubular aggregate myopathy (TAM) characterized by muscular pain, weakness and cramping. TAM-associated mutations in ORAI1 first and third transmembrane domain facilitate channel opening by STIM1, causing constitutive Ca2+ influx and increasing the currents evoked by Ca2+ store depletion. Mutation V107M additionally decreases the channel selectivity for Ca2+ ions and its inhibition by acidic pH, while mutation T184M does not alter the channel sensitivity to pH or to reactive oxygen species. The ORAI blocker GSK-7975A prevents the constitutive activity of TAM-associated channels and might be used in therapy for patients suffering from TAM. ABSTRACT Skeletal muscle differentiation relies on store-operated Ca2+ entry (SOCE) mediated by STIM proteins linking the depletion of endoplasmic/sarcoplasmic reticulum Ca2+ stores to the activation of membrane Ca2+ -permeable ORAI channels. Gain-of-function mutations in STIM1 or ORAI1 isoforms cause tubular aggregate myopathy (TAM), a skeletal muscle disorder with muscular pain, weakness and cramping. Here, we characterize two overactive ORAI1 mutants from patients with TAM: V107M and T184M, located in the first and third transmembrane domain of the channel. When ectopically expressed in HEK-293T cells or human primary myoblasts, the mutated channels increased basal and store-operated Ca2+ entry. The constitutive activity of V107M, L138F, T184M and P245L mutants was prevented by low concentrations of GSK-7975A while the G98S mutant was resistant to inhibition. Electrophysiological recordings confirmed ORAI1-V107M constitutive activity and revealed larger STIM1-gated V107M- and T184M-mediated currents with conserved fast and slow Ca2+ -dependent inactivation. Mutation V107M altered the channel selectivity for Ca2+ ions and conferred resistance to acidic inhibition. Ca2+ imaging and molecular dynamics simulations showed a preserved sensitivity of T184M to the negative regulation by reactive oxygen species. Both mutants were able to mediate SOCE in Stim1-/- /Stim2-/- mouse embryonic fibroblasts expressing the binding-deficient STIM1-F394H mutant, indicating a higher sensitivity for STIM1-mediated gating, with ORAI1-T184M gain-of-function being strictly dependent on STIM1. These findings provide new insights into the permeation and regulatory properties of ORAI1 mutants that might translate into therapies against diseases with gain-of-function mutations in ORAI1.
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Affiliation(s)
- M Bulla
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - G Gyimesi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - J H Kim
- Departments of Physiology and Global Medical Science, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.,Mitohormesis Research Center, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - R Bhardwaj
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - M A Hediger
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - M Frieden
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - N Demaurex
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
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13
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Wu G, Yang X, Shen Y. Identification of a single aspartate residue critical for both fast and slow calcium-dependent inactivation of the human TRPML1 channel. J Biol Chem 2018; 293:11736-11745. [PMID: 29884771 DOI: 10.1074/jbc.ra118.003250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 06/05/2018] [Indexed: 01/16/2023] Open
Abstract
Transient receptor potential mucolipin subfamily 1 (TRPML1) is a nonselective cation channel mainly located in late endosomes and lysosomes. Mutations of the gene encoding human TRPML1 can cause severe lysosomal diseases. The activity of TRPML1 is regulated by both Ca2+ and H+, which are important for its critical physiological functions in membrane trafficking, exocytosis, autophagy, and intracellular signal transduction. However, the molecular mechanism of its dual regulation by Ca2+ and H+ remains elusive. Here, using a mutant screening method in combination with a whole-cell patch clamp technique, we identified a key TRPML1 residue, Asp-472, responsible for both fast calcium-dependent inactivation (FCDI) and slow calcium-dependent inactivation (SCDI) as well as H+ regulation. We also found that, in acidic pH, H+ can significantly delay FCDI and abolish SCDI and thereby presumably facilitate the ion conductance of the human TRPML1 channel. In summary, we have identified a key residue critical for Ca2+-induced inhibition of TRPML1 channel currents and uncovered pH-dependent regulation of this channel, providing vital information regarding the detailed mechanism of action of human TRPML1.
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Affiliation(s)
- Guangyan Wu
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and
| | - Xue Yang
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and
| | - Yuequan Shen
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and .,the Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin 300071, China
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14
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Fine-tuning of store-operated calcium entry by fast and slow Ca 2+-dependent inactivation: Involvement of SARAF. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1865:463-469. [PMID: 29223474 DOI: 10.1016/j.bbamcr.2017.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 12/02/2017] [Accepted: 12/04/2017] [Indexed: 02/07/2023]
Abstract
Store-operated Ca2+ entry (SOCE) is a functionally relevant mechanism for Ca2+ influx present in electrically excitable and non-excitable cells. Regulation of Ca2+ entry through store-operated channels is essential to maintain an appropriate intracellular Ca2+ homeostasis and prevent cell damage. Calcium-release activated channels exhibit Ca2+-dependent inactivation mediated by two temporally separated mechanisms: fast Ca2+-dependent inactivation takes effect in the order of milliseconds and involves the interaction of Ca2+ with residues in the channel pore while slow Ca2+-dependent inactivation (SCDI) develops over tens of seconds, requires a global rise in [Ca2+]cyt and is a mechanism regulated by mitochondria. Recent studies have provided evidence that the protein SARAF (SOCE-associated regulatory factor) is involved in the mechanism underlying SCDI of Orai1. SARAF is an endoplasmic reticulum (ER) membrane protein that associates with STIM1 and translocate to plasma membrane-ER junctions in a STIM1-dependent manner upon store depletion to modulate SOCE. SCDI mediated by SARAF depends on the location of the STIM1-Orai1 complex within a PI(4,5)P2-rich microdomain. SARAF also interacts with Orai1 and TRPC1 in cells endogenously expressing STIM1 and cells with a low STIM1 expression and modulates channel function. This review focuses on the modulation by SARAF of SOCE and other forms of Ca2+ influx mediated by Orai1 and TRPC1 in order to provide spatio-temporally regulated Ca2+ signals.
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15
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Li X, Wu G, Yang Y, Fu S, Liu X, Kang H, Yang X, Su XC, Shen Y. Calmodulin dissociates the STIM1-Orai1 complex and STIM1 oligomers. Nat Commun 2017; 8:1042. [PMID: 29051492 PMCID: PMC5648805 DOI: 10.1038/s41467-017-01135-w] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Accepted: 08/22/2017] [Indexed: 01/20/2023] Open
Abstract
Store-operated calcium entry (SOCE) is a major pathway for calcium ions influx into cells and has a critical role in various cell functions. Here we demonstrate that calcium-bound calmodulin (Ca2+-CaM) binds to the core region of activated STIM1. This interaction facilitates slow Ca2+-dependent inactivation after Orai1 channel activation by wild-type STIM1 or a constitutively active STIM1 mutant. We define the CaM-binding site in STIM1, which is adjacent to the STIM1-Orai1 coupling region. The binding of Ca2+-CaM to activated STIM1 disrupts the STIM1-Orai1 complex and also disassembles STIM1 oligomer. Based on these results we propose a model for the calcium-bound CaM-regulated deactivation of SOCE.
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Affiliation(s)
- Xin Li
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin, 300071, China
| | - Guangyan Wu
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin, 300071, China
| | - Yin Yang
- State Key Laboratory of Elemento-Organic Chemistry and College of Chemistry, Nankai University, 94 Weijin Road, Tianjin, 300071, China
| | - Shijuan Fu
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin, 300071, China
| | - Xiaofen Liu
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin, 300071, China
| | - Huimin Kang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin, 300071, China
| | - Xue Yang
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin, 300071, China.
| | - Xun-Cheng Su
- State Key Laboratory of Elemento-Organic Chemistry and College of Chemistry, Nankai University, 94 Weijin Road, Tianjin, 300071, China. .,Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin, 300071, China.
| | - Yuequan Shen
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin, 300071, China. .,Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin, 300071, China.
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16
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Bravo-Sagua R, Parra V, López-Crisosto C, Díaz P, Quest AFG, Lavandero S. Calcium Transport and Signaling in Mitochondria. Compr Physiol 2017; 7:623-634. [PMID: 28333383 DOI: 10.1002/cphy.c160013] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Calcium (Ca2+) is a key player in the regulation of many cell functions. Just like Ca2+, mitochondria are ubiquitous, versatile, and dynamic players in determining both cell survival and death decisions. Given their ubiquitous nature, the regulation of both is deeply intertwined, whereby Ca2+ regulates mitochondrial functions, while mitochondria shape Ca2+ dynamics. Deregulation of either Ca2+ or mitochondrial signaling leads to abnormal function, cell damage or even cell death, thereby contributing to muscle dysfunction or cardiac pathologies. Moreover, altered mitochondrial Ca2+ homeostasis has been linked to metabolic diseases like cancer, obesity, and pulmonary hypertension. In this review article, we summarize the mechanisms that coordinate mitochondrial and Ca2+ responses and how they affect human health. © 2017 American Physiological Society. Compr Physiol 7:623-634, 2017.
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Affiliation(s)
- Roberto Bravo-Sagua
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile.,Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago, Chile
| | - Valentina Parra
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Camila López-Crisosto
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Paula Díaz
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Andrew F G Quest
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile.,Center for Molecular Studies of the Cell (CEMC), Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile
| | - Sergio Lavandero
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile.,Center for Molecular Studies of the Cell (CEMC), Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile.,Cardiology Division, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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17
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Spät A, Szanda G. The Role of Mitochondria in the Activation/Maintenance of SOCE: Store-Operated Ca 2+ Entry and Mitochondria. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:257-275. [PMID: 28900919 DOI: 10.1007/978-3-319-57732-6_14] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mitochondria extensively modify virtually all cellular Ca2+ transport processes, and store-operated Ca2+ entry (SOCE) is no exception to this rule. The interaction between SOCE and mitochondria is complex and reciprocal, substantially altering and, ultimately, fine-tuning both capacitative Ca2+ influx and mitochondrial function. Mitochondria, owing to their considerable Ca2+ accumulation ability, extensively buffer the cytosolic Ca2+ in their vicinity. In turn, the accumulated ion is released back into the neighboring cytosol during net Ca2+ efflux. Since store depletion itself and the successive SOCE are both Ca2+-regulated phenomena, mitochondrial Ca2+ handling may have wide-ranging effects on capacitative Ca2+ influx at any given time. In addition, mitochondria may also produce or consume soluble factors known to affect store-operated channels. On the other hand, Ca2+ entering the cell during SOCE is sensed by mitochondria, and the ensuing mitochondrial Ca2+ uptake boosts mitochondrial energy metabolism and, if Ca2+ overload occurs, may even lead to apoptosis or cell death. In several cell types, mitochondria seem to be sterically excluded from the confined space that forms between the plasma membrane (PM) and endoplasmic reticulum (ER) during SOCE. This implies that high-Ca2+ microdomains comparable to those observed between the ER and mitochondria do not form here. In the following chapter, the above aspects of the many-sided SOCE-mitochondrion interplay will be discussed in greater detail.
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Affiliation(s)
- András Spät
- Department of Physiology, Semmelweis University Medical School, POB 2, 1428, Budapest, Hungary.
- Laboratory of Molecular Physiology, Hungarian Academy of Sciences, Budapest, Hungary.
| | - Gergö Szanda
- Department of Physiology, Semmelweis University Medical School, POB 2, 1428, Budapest, Hungary
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18
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Pacheco J, Vaca L. STIM-TRP Pathways and Microdomain Organization: Auxiliary Proteins of the STIM/Orai Complex. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:189-210. [DOI: 10.1007/978-3-319-57732-6_10] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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19
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Malli R, Graier WF. The Role of Mitochondria in the Activation/Maintenance of SOCE: The Contribution of Mitochondrial Ca 2+ Uptake, Mitochondrial Motility, and Location to Store-Operated Ca 2+ Entry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:297-319. [PMID: 28900921 DOI: 10.1007/978-3-319-57732-6_16] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In most cell types, the depletion of internal Ca2+ stores triggers the activation of Ca2+ entry. This crucial phenomenon is known since the 1980s and referred to as store-operated Ca2+ entry (SOCE). With the discoveries of the stromal-interacting molecules (STIMs) and the Ca2+-permeable Orai channels as the long-awaited molecular constituents of SOCE, the role of mitochondria in controlling the activity of this particular Ca2+ entry pathway is kind of buried in oblivion. However, the capability of mitochondria to locally sequester Ca2+ at sites of Ca2+ release and entry was initially supposed to rule SOCE by facilitating the Ca2+ depletion of the endoplasmic reticulum and removing entering Ca2+ from the Ca2+-inhibitable channels, respectively. Moreover, the central role of these organelles in controlling the cellular energy metabolism has been linked to the activity of SOCE. Nevertheless, the exact molecular mechanisms by which mitochondria actually determine SOCE are still pretty obscure. In this essay we describe the complexity of the mitochondrial Ca2+ uptake machinery and its regulation, molecular components, and properties, which open new ways for scrutinizing the contribution of mitochondria to SOCE. Moreover, data concerning the variability of the morphology and cellular distribution of mitochondria as putative determinants of SOCE activation, maintenance, and termination are summarized.
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Affiliation(s)
- Roland Malli
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstrasse 6/6, 8010, Graz, Austria
| | - Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstrasse 6/6, 8010, Graz, Austria.
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20
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Parekh AB. Regulation of CRAC channels by Ca 2+-dependent inactivation. Cell Calcium 2016; 63:20-23. [PMID: 28043696 DOI: 10.1016/j.ceca.2016.12.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 12/14/2016] [Accepted: 12/15/2016] [Indexed: 12/27/2022]
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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21
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Nita II, Caspi Y, Gudes S, Fishman D, Lev S, Hersfinkel M, Sekler I, Binshtok AM. Privileged crosstalk between TRPV1 channels and mitochondrial calcium shuttling machinery controls nociception. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2868-2880. [DOI: 10.1016/j.bbamcr.2016.09.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 09/06/2016] [Accepted: 09/09/2016] [Indexed: 10/21/2022]
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22
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Albarran L, Lopez JJ, Amor NB, Martin-Cano FE, Berna-Erro A, Smani T, Salido GM, Rosado JA. Dynamic interaction of SARAF with STIM1 and Orai1 to modulate store-operated calcium entry. Sci Rep 2016; 6:24452. [PMID: 27068144 PMCID: PMC4828706 DOI: 10.1038/srep24452] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 03/30/2016] [Indexed: 12/16/2022] Open
Abstract
Ca(2+) influx by store-operated Ca(2+) channels is a major mechanism for intracellular Ca(2+) homeostasis and cellular function. Here we present evidence for the dynamic interaction between the SOCE-associated regulatory factor (SARAF), STIM1 and Orai1. SARAF overexpression attenuated SOCE and the STIM1-Orai1 interaction in cells endogenously expressing STIM1 and Orai1 while RNAi-mediated SARAF silencing induced opposite effects. SARAF impaired the association between Orai1 and the Orai1-activating small fragment of STIM1 co-expressed in the STIM1-deficient NG115-401L cells. Cell treatment with thapsigargin or physiological agonists results in direct association of SARAF with Orai1. STIM1-independent interaction of SARAF with Orai1 leads to activation of this channel. In cells endogenously expressing STIM1 and Orai1, Ca(2+) store depletion leads to dissociation of SARAF with STIM1 approximately 30s after treatment with thapsigargin, which paralleled the increase in SARAF-Orai1 interaction, followed by reinteraction with STIM1 and dissociation from Orai1. Co-expression of SARAF and either Orai1 or various N-terminal deletion Orai1 mutants did not alter SARAF-Orai1 interaction; however, expression of C-terminal deletion Orai1 mutants or blockade of the C-terminus of Orai1 impair the interaction with SARAF. These observations suggest that SARAF exerts an initial positive role in the activation of SOCE followed by the facilitation of SCDI of Orai1.
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Affiliation(s)
- Letizia Albarran
- Department of Physiology (Cellular Physiology and Muscle Physiology Research Groups), University of Extremadura, 10003 Cáceres, Spain
| | - Jose J Lopez
- Department of Physiology (Cellular Physiology and Muscle Physiology Research Groups), University of Extremadura, 10003 Cáceres, Spain
| | - Nidhal Ben Amor
- Department of Physiology (Cellular Physiology and Muscle Physiology Research Groups), University of Extremadura, 10003 Cáceres, Spain
| | - Francisco E Martin-Cano
- Department of Physiology (Cellular Physiology and Muscle Physiology Research Groups), University of Extremadura, 10003 Cáceres, Spain
| | - Alejandro Berna-Erro
- Department of Physiology (Cellular Physiology and Muscle Physiology Research Groups), University of Extremadura, 10003 Cáceres, Spain
| | - Tarik Smani
- Department of Medical Physiology and Biophysics, Institute of Biomedicine of Sevilla, Sevilla, Spain
| | - Gines M Salido
- Department of Physiology (Cellular Physiology and Muscle Physiology Research Groups), University of Extremadura, 10003 Cáceres, Spain
| | - Juan A Rosado
- Department of Physiology (Cellular Physiology and Muscle Physiology Research Groups), University of Extremadura, 10003 Cáceres, Spain
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23
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Cheng W, Zhu Y, Wang H. The MAPK pathway is involved in the regulation of rapid pacing-induced ionic channel remodeling in rat atrial myocytes. Mol Med Rep 2016; 13:2677-82. [PMID: 26847818 DOI: 10.3892/mmr.2016.4862] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Accepted: 01/11/2016] [Indexed: 11/06/2022] Open
Abstract
Alterations to the expression L‑type calcium channels (LTCCs) and Kv4.3 potassium channels form the possible basis of atrial electrical remodeling during rapid pacing. The mitogen‑activated protein kinase (MAPK) pathway is affected by increases in cytoplasmic Ca2+, and therefore represents an attractive candidate for the regulation and mediation of Ca2+‑induced ion channel remodeling. The present study aimed to investigate alterations to the ion channel‑MAPK axis, and to determine its influence on ion channel remodeling during atrial fibrillation. Rat atrial myocytes were isolated, cultured, and in vitro rapid pacing was established. Intracellular Ca2+ signals were monitored using the Fluo‑3/AM Ca2+ indicator. Verapamil, PD98058 and SB203580 were added to the culture medium of various groups at specific time‑points. The mRNA expression levels of LTCC‑α1c and Kv4.3 potassium channels were detected by reverse transcription‑polymerase chain reaction. Western blotting was performed to determine the expression levels of channel and signaling proteins. The results demonstrated that fast pacing significantly increased the intracellular Ca2+ concentration in atrial myocytes, whereas treatment with verapamil markedly inhibited this increase. In addition, verapamil significantly antagonized the rapid pacing‑induced activation of extracellular signal‑regulated kinase (ERK) and p38MAPK. These results indicated that the MAPK pathway may have an important role in the opening of LTCCs, and alterations to MAPK molecule expression could affect the expression and remodeling of ion channels.
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Affiliation(s)
- Wei Cheng
- Department of Cardiothoracic Surgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China
| | - Yun Zhu
- Department of Cardiothoracic Surgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China
| | - Haidong Wang
- Department of Cardiothoracic Surgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China
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24
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Abstract
Store-operated calcium channels (SOCs) are a major pathway for calcium signaling in virtually all metozoan cells and serve a wide variety of functions ranging from gene expression, motility, and secretion to tissue and organ development and the immune response. SOCs are activated by the depletion of Ca(2+) from the endoplasmic reticulum (ER), triggered physiologically through stimulation of a diverse set of surface receptors. Over 15 years after the first characterization of SOCs through electrophysiology, the identification of the STIM proteins as ER Ca(2+) sensors and the Orai proteins as store-operated channels has enabled rapid progress in understanding the unique mechanism of store-operate calcium entry (SOCE). Depletion of Ca(2+) from the ER causes STIM to accumulate at ER-plasma membrane (PM) junctions where it traps and activates Orai channels diffusing in the closely apposed PM. Mutagenesis studies combined with recent structural insights about STIM and Orai proteins are now beginning to reveal the molecular underpinnings of these choreographic events. This review describes the major experimental advances underlying our current understanding of how ER Ca(2+) depletion is coupled to the activation of SOCs. Particular emphasis is placed on the molecular mechanisms of STIM and Orai activation, Orai channel properties, modulation of STIM and Orai function, pharmacological inhibitors of SOCE, and the functions of STIM and Orai in physiology and disease.
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Affiliation(s)
- Murali Prakriya
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; and Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California
| | - Richard S Lewis
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; and Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California
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25
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Store-operated calcium entry: Mechanisms and modulation. Biochem Biophys Res Commun 2015; 460:40-9. [PMID: 25998732 DOI: 10.1016/j.bbrc.2015.02.110] [Citation(s) in RCA: 152] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 02/20/2015] [Indexed: 11/22/2022]
Abstract
Store-operated calcium entry is a central mechanism in cellular calcium signalling and in maintaining cellular calcium balance. This review traces the history of research on store-operated calcium entry, the discovery of STIM and ORAI as central players in calcium entry, and the role of STIM and ORAI in biology and human disease. It describes current knowledge of the basic mechanism of STIM-ORAI signalling and of the varied mechanisms by which STIM-ORAI signalling can be modulated.
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26
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Schurr JM. A Possible Cooperative Structural Transition of DNA in the 0.25–2.0 pN Range. J Phys Chem B 2015; 119:6389-400. [DOI: 10.1021/acs.jpcb.5b03174] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J. Michael Schurr
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
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27
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Distinct structural domains of caveolin-1 independently regulate Ca2+ release-activated Ca2+ channels and Ca2+ microdomain-dependent gene expression. Mol Cell Biol 2015; 35:1341-9. [PMID: 25645930 DOI: 10.1128/mcb.01068-14] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In eukaryotic cells, calcium entry across the cell surface activates nuclear gene expression, a process critically important for cell growth and differentiation, learning, and memory and immune cell functions. In immune cells, calcium entry occurs through store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels, comprised of STIM1 and Orai1 proteins. Local calcium entry through CRAC channels activates expression of c-fos- and nuclear factor of activated T cells (NFAT)-dependent genes. Although c-fos and NFAT often interact to activate gene expression synergistically, they can be activated independently of one another to regulate distinct genes. This raises the question of how one transcription factor can be activated and not the other when both are stimulated by the same trigger. Here, we show that the lipid raft scaffolding protein caveolin-1 interacts with the STIM1-Orai1 complex to increase channel activity. Phosphorylation of tyrosine 14 on caveolin-1 regulates CRAC channel-evoked c-fos activation without impacting the NFAT pathway or Orai1 activity. Our results reveal that structurally distinct domains of caveolin-1 selectively regulate the ability of local calcium to activate distinct transcription factors. More generally, our findings reveal that modular regulation by a scaffolding protein provides a simple, yet effective, mechanism to tunnel a local signal down a specific pathway.
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28
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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: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [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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29
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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] [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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30
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Srikanth S, Gwack Y. Molecular regulation of the pore component of CRAC channels, Orai1. CURRENT TOPICS IN MEMBRANES 2014; 71:181-207. [PMID: 23890116 DOI: 10.1016/b978-0-12-407870-3.00008-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Abstract
Store-operated Ca(2+) entry (SOCE) is a fundamental mechanism ubiquitously employed by cells to elevate intracellular Ca(2+) concentrations ([Ca(2+)]i). Increased intracellular Ca(2+) ions act as a second messenger that can stimulate a variety of downstream signaling pathways affecting proliferation, secretion, differentiation, and death of cells. In immune cells, immune receptor stimulation induces endoplasmic reticulum Ca(2+) store depletion that subsequently activates Ca(2+)-release-activated-Ca(2+) (CRAC) channels, a prototype of store-operated Ca(2+) (SOC) channels. Identification of Orai1 as the pore subunit of CRAC channels has provided the much-needed molecular tool to dissect the mechanism of activation and regulation of these channels. In this review, we discuss the recent advances in understanding the regulatory mechanisms and posttranslational modifications that regulate diverse aspects of CRAC channel function.
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Affiliation(s)
- Sonal Srikanth
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
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Jairaman A, Prakriya M. Molecular pharmacology of store-operated CRAC channels. Channels (Austin) 2013; 7:402-14. [PMID: 23807116 DOI: 10.4161/chan.25292] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Calcium influx through store-operated Ca(2+) release-activated Ca(2+) channels (CRAC channels) is a well-defined mechanism of generating cellular Ca(2+) elevations that regulates many functions including gene expression, exocytosis and cell proliferation. The identifications of the ER Ca(2+) sensing proteins, STIM1-2 and the CRAC channel proteins, Orai1-3, have led to improved understanding of the physiological roles and the activation mechanism of CRAC channels. Defects in CRAC channel function are associated with serious human diseases such as immunodeficiency and auto-immunity. In this review, we discuss several pharmacological modulators of CRAC channels, focusing specifically on the molecular mechanism of drug action and their utility in illuminating the mechanism of CRAC channel operation and their physiological roles in different cells.
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Affiliation(s)
- Amit Jairaman
- Department of Molecular Pharmacology and Biological Chemistry; Northwestern University, Feinberg School of Medicine; Chicago, IL USA
| | - Murali Prakriya
- Department of Molecular Pharmacology and Biological Chemistry; Northwestern University, Feinberg School of Medicine; Chicago, IL USA
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Joseph N, Reicher B, Barda-Saad M. The calcium feedback loop and T cell activation: how cytoskeleton networks control intracellular calcium flux. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:557-68. [PMID: 23860253 DOI: 10.1016/j.bbamem.2013.07.009] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 06/30/2013] [Accepted: 07/08/2013] [Indexed: 12/31/2022]
Abstract
During T cell activation, the engagement of a T cell with an antigen-presenting cell (APC) results in rapid cytoskeletal rearrangements and a dramatic increase of intracellular calcium (Ca(2+)) concentration, downstream to T cell antigen receptor (TCR) ligation. These events facilitate the organization of an immunological synapse (IS), which supports the redistribution of receptors, signaling molecules and organelles towards the T cell-APC interface to induce downstream signaling events, ultimately supporting T cell effector functions. Thus, Ca(2+) signaling and cytoskeleton rearrangements are essential for T cell activation and T cell-dependent immune response. Rapid release of Ca(2+) from intracellular stores, e.g. the endoplasmic reticulum (ER), triggers the opening of Ca(2+) release-activated Ca(2+) (CRAC) channels, residing in the plasma membrane. These channels facilitate a sustained influx of extracellular Ca(2+) across the plasma membrane in a process termed store-operated Ca(2+) entry (SOCE). Because CRAC channels are themselves inhibited by Ca(2+) ions, additional factors are suggested to enable the sustained Ca(2+) influx required for T cell function. Among these factors, we focus here on the contribution of the actin and microtubule cytoskeleton. The TCR-mediated increase in intracellular Ca(2+) evokes a rapid cytoskeleton-dependent polarization, which involves actin cytoskeleton rearrangements and microtubule-organizing center (MTOC) reorientation. Here, we review the molecular mechanisms of Ca(2+) flux and cytoskeletal rearrangements, and further describe the way by which the cytoskeletal networks feedback to Ca(2+) signaling by controlling the spatial and temporal distribution of Ca(2+) sources and sinks, modulating TCR-dependent Ca(2+) signals, which are required for an appropriate T cell response. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
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Affiliation(s)
- Noah Joseph
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Barak Reicher
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Mira Barda-Saad
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
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Jha A, Ahuja M, Maléth J, Moreno CM, Yuan JP, Kim MS, Muallem S. The STIM1 CTID domain determines access of SARAF to SOAR to regulate Orai1 channel function. ACTA ACUST UNITED AC 2013; 202:71-9. [PMID: 23816623 PMCID: PMC3704993 DOI: 10.1083/jcb.201301148] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two distinct lobes in the C-terminal inhibitory domain in STIM1 determine access of the inhibitor SARAF to the activating SOAR domain to regulate the slow Ca2+-dependent inactivation of Orai1. Ca2+ influx by store-operated Ca2+ channels (SOCs) mediates all Ca2+-dependent cell functions, but excess Ca2+ influx is highly toxic. The molecular components of SOC are the pore-forming Orai1 channel and the endoplasmic reticulum Ca2+ sensor STIM1. Slow Ca2+-dependent inactivation (SCDI) of Orai1 guards against cell damage, but its molecular mechanism is unknown. Here, we used homology modeling to identify a conserved STIM1(448–530) C-terminal inhibitory domain (CTID), whose deletion resulted in spontaneous clustering of STIM1 and full activation of Orai1 in the absence of store depletion. CTID regulated SCDI by determining access to and interaction of the STIM1 inhibitor SARAF with STIM1 Orai1 activation region (SOAR), the STIM1 domain that activates Orai1. CTID had two lobes, STIM1(448–490) and STIM1(490–530), with distinct roles in mediating access of SARAF to SOAR. The STIM1(448–490) lobe restricted, whereas the STIM1(490–530) lobe directed, SARAF to SOAR. The two lobes cooperated to determine the features of SCDI. These findings highlight the central role of STIM1 in SCDI and provide a molecular mechanism for SCDI of Orai1.
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Affiliation(s)
- Archana Jha
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
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Mitochondrial regulation of CRAC channel-driven cellular responses. Cell Calcium 2012; 52:52-6. [DOI: 10.1016/j.ceca.2012.02.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 02/08/2012] [Accepted: 02/09/2012] [Indexed: 11/15/2022]
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SARAF Inactivates the Store Operated Calcium Entry Machinery to Prevent Excess Calcium Refilling. Cell 2012; 149:425-38. [DOI: 10.1016/j.cell.2012.01.055] [Citation(s) in RCA: 200] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 11/24/2011] [Accepted: 01/26/2012] [Indexed: 11/17/2022]
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36
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Cysteinyl leukotriene type I receptor desensitization sustains Ca2+-dependent gene expression. Nature 2012; 482:111-5. [PMID: 22230957 PMCID: PMC3272478 DOI: 10.1038/nature10731] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 11/23/2011] [Indexed: 12/03/2022]
Abstract
A universal mechanism to turn off a biological response is receptor desensitization, where the ability of a physiological trigger to activate a cell is lost despite the continued presence of the stimulus. Receptor desensitization of G protein-coupled receptors involves uncoupling of the receptor from its G protein/second messenger pathway, followed by receptor internalization1. G protein-coupled cysteinyl leukotriene type I (CysLT1) receptors regulate immune cell function and the receptor is an established therapeutic target for allergies including asthma2. Desensitization of these receptors arises predominantly from protein kinase C-dependent phosphorylation of three serine residues in the receptor C-terminus3. Physiological concentrations of the receptor agonist LTC4 evoke repetitive cytoplasmic Ca2+ oscillations, reflecting regenerative Ca2+ release from stores that is sustained by Ca2+ entry through store-operated CRAC channels4. CRAC channels are tightly linked to expression of the transcription factor c-fos5, a regulator of numerous genes important to cell growth and development6. Here we show that abolishing leukotriene receptor desensitization suppresses agonist-driven gene expression. Mechanistically, stimulation of non-desensitizing receptors evoked prolonged inositol trisphosphate-mediated Ca2+ release, which led to accelerated Ca2+-dependent slow inactivation of CRAC channels and a subsequent loss of excitation-transcription coupling. Rather than serving to turn off a biological response, reversible desensitization of a Ca2+ mobilizing receptor acts as an ‘on’switch, sustaining long-term signalling in the immune system.
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37
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The hepatitis B virus X protein elevates cytosolic calcium signals by modulating mitochondrial calcium uptake. J Virol 2011; 86:313-27. [PMID: 22031934 DOI: 10.1128/jvi.06442-11] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Chronic hepatitis B virus (HBV) infections are associated with the development of hepatocellular carcinoma (HCC). The HBV X protein (HBx) is thought to play an important role in the development of HBV-associated HCC. One fundamental HBx function is elevation of cytosolic calcium signals; this HBx activity has been linked to HBx stimulation of cell proliferation and transcription pathways, as well as HBV replication. Exactly how HBx elevates cytosolic calcium signals is not clear. The studies described here show that HBx stimulates calcium entry into cells, resulting in an increased plateau level of inositol 1,4,5-triphosphate (IP3)-linked calcium signals. This increased calcium plateau can be inhibited by blocking mitochondrial calcium uptake and store-operated calcium entry (SOCE). Blocking SOCE also reduced HBV replication. Finally, these studies also demonstrate that there is increased mitochondrial calcium uptake in HBx-expressing cells. Cumulatively, these studies suggest that HBx can increase mitochondrial calcium uptake and promote increased SOCE to sustain higher cytosolic calcium and stimulate HBV replication.
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Store-operated Ca2+ entry in sensory neurons: functional role and the effect of painful nerve injury. J Neurosci 2011; 31:3536-49. [PMID: 21389210 DOI: 10.1523/jneurosci.5053-10.2011] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Painful nerve injury disrupts levels of cytoplasmic and stored Ca(2+) in sensory neurons. Since influx of Ca(2+) may occur through store-operated Ca(2+) entry (SOCE) as well as voltage- and ligand-activated pathways, we sought confirmation of SOCE in sensory neurons from adult rats and examined whether dysfunction of SOCE is a possible pathogenic mechanism. Dorsal root ganglion neurons displayed a fall in resting cytoplasmic Ca(2+) concentration when bath Ca(2+) was withdrawn, and a subsequent elevation of cytoplasmic Ca(2+) concentration (40 ± 5 nm) when Ca(2+) was reintroduced, which was amplified by store depletion with thapsigargin (1 μm), and was significantly reduced by blockers of SOCE, but was unaffected by antagonists of voltage-gated membrane Ca(2+) channels. We identified the underlying inwardly rectifying Ca(2+)-dependent I(CRAC) (Ca(2+) release activated current), as well as a large thapsigargin-sensitive inward current activated by withdrawal of bath divalent cations, representing SOCE. Molecular components of SOCE, specifically STIM1 and Orai1, were confirmed in sensory neurons at both the transcript and protein levels. Axonal injury by spinal nerve ligation (SNL) elevated SOCE and I(CRAC). However, SOCE was comparable in injured and control neurons when stores were maximally depleted by thapsigargin, and STIM1 and Orai1 levels were not altered by SNL, showing that upregulation of SOCE after SNL is driven by store depletion. Blockade of SOCE increased neuronal excitability in control and injured neurons, whereas injured neurons showed particular dependence on SOCE for maintaining levels of cytoplasmic and stored Ca(2+), which indicates a compensatory role for SOCE after injury.
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39
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Pradhan RK, Qi F, Beard DA, Dash RK. Characterization of membrane potential dependency of mitochondrial Ca2+ uptake by an improved biophysical model of mitochondrial Ca2+ uniporter. PLoS One 2010; 5:e13278. [PMID: 20949039 PMCID: PMC2951907 DOI: 10.1371/journal.pone.0013278] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Accepted: 09/13/2010] [Indexed: 02/02/2023] Open
Abstract
Mitochondrial Ca2+ uniporter is the primary influx pathway for Ca2+ into respiring mitochondria, and hence plays a key role in mitochondrial Ca2+ homeostasis. Though the mechanism of extra-matrix Ca2+ dependency of mitochondrial Ca2+ uptake has been well characterized both experimentally and mathematically, the mechanism of membrane potential (ΔΨ) dependency of mitochondrial Ca2+ uptake has not been completely characterized. In this paper, we perform a quantitative reevaluation of a previous biophysical model of mitochondrial Ca2+ uniporter that characterized the possible mechanism of ΔΨ dependency of mitochondrial Ca2+ uptake. Based on a model simulation analysis, we show that model predictions with a variant assumption (Case 2: external and internal Ca2+ binding constants for the uniporter are distinct), that provides the best possible description of the ΔΨ dependency, are highly sensitive to variation in matrix [Ca2+], indicating limitations in the variant assumption (Case 2) in providing physiologically plausible description of the observed ΔΨ dependency. This sensitivity is attributed to negative estimate of a biophysical parameter that characterizes binding of internal Ca2+ to the uniporter. Reparameterization of the model with additional nonnengativity constraints on the biophysical parameters showed that the two variant assumptions (Case 1 and Case 2) are indistinguishable, indicating that the external and internal Ca2+ binding constants for the uniporter may be equal (Case 1). The model predictions in this case are insensitive to variation in matrix [Ca2+] but do not match the ΔΨ dependent data in the domain ΔΨ≤120 mV. To effectively characterize this ΔΨ dependency, we reformulate the ΔΨ dependencies of the rate constants of Ca2+ translocation via the uniporter by exclusively redefining the biophysical parameters associated with the free-energy barrier of Ca2+ translocation based on a generalized, non-linear Goldman-Hodgkin-Katz formulation. This alternate uniporter model has all the characteristics of the previous uniporter model and is also able to characterize the possible mechanisms of both the extra-matrix Ca2+ and ΔΨ dependencies of mitochondrial Ca2+ uptake. In addition, the model is insensitive to variation in matrix [Ca2+], predicting relatively stable physiological operation. The model is critical in developing mechanistic, integrated models of mitochondrial bioenergetics and Ca2+ handling.
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Affiliation(s)
- Ranjan K. Pradhan
- Biotechnology and Bioengineering Center and Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Feng Qi
- Biotechnology and Bioengineering Center and Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Daniel A. Beard
- Biotechnology and Bioengineering Center and Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Ranjan K. Dash
- Biotechnology and Bioengineering Center and Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
- * E-mail:
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40
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Tekmen M, Gleason E. Multiple Ca2+-dependent mechanisms regulate L-type Ca2+ current in retinal amacrine cells. J Neurophysiol 2010; 104:1849-66. [PMID: 20685929 DOI: 10.1152/jn.00031.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Understanding the regulation of L-type voltage-gated Ca(2+) current is an important component of elucidating the signaling capabilities of retinal amacrine cells. Here we ask how the cytosolic Ca(2+) environment and the balance of Ca(2+)-dependent effectors shape native L-type Ca(2+) channel function in these cells. To achieve this, whole cell voltage clamp recordings were made from cultured amacrine cells under conditions that address the contribution of mitochondrial Ca(2+) uptake (MCU), Ca(2+)/calmodulin (CaM)-dependent channel inactivation (CDI), protein kinase A (PKA), and Ca(2+)-induced Ca(2+) release (CICR). Under control conditions, repeated activation of the L-type channels produces a progressive enhancement of the current. Inhibition of MCU causes a reduction in the Ca(2+) current amplitude that is dependent on Ca(2+) influx as well as cytosolic Ca(2+) buffering, consistent with CDI. Including the Ca(2+) buffer bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) internally can shift the balance between enhancement and inhibition such that inhibition of MCU can enhance the current. Inhibition of PKA can remove the enhancing effect of BAPTA suggesting that cyclic AMP-dependent phosphorylation is involved. Inhibition of CaM suppresses CDI but spares the enhancement, consistent with the substantially higher sensitivity of the Ca(2+)-sensitive adenylate cyclase 1 (AC1) to Ca(2+)/CaM. Inhibition of the ryanodine receptor reduces the current amplitude, suggesting that CICR might normally amplify the activation of AC1 and stimulation of PKA activity. These experiments reveal that the amplitude of L-type Ca(2+) currents in retinal amacrine cells are both positively and negatively regulated by Ca(2+)-dependent mechanisms.
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Affiliation(s)
- Merve Tekmen
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
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41
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Naghdi S, Waldeck-Weiermair M, Fertschai I, Poteser M, Graier WF, Malli R. Mitochondrial Ca2+ uptake and not mitochondrial motility is required for STIM1-Orai1-dependent store-operated Ca2+ entry. J Cell Sci 2010; 123:2553-64. [DOI: 10.1242/jcs.070151] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Store-operated Ca2+ entry (SOCE) is established by formation of subplasmalemmal clusters of the endoplasmic reticulum (ER) protein, stromal interacting molecule 1 (STIM1) upon ER Ca2+ depletion. Thereby, STIM1 couples to plasma membrane channels such as Orai1. Thus, a close proximity of ER domains to the plasma membrane is a prerequisite for SOCE activation, challenging the concept of local Ca2+ buffering by mitochondria as being essential for SOCE. This study assesses the impact of mitochondrial Ca2+ handling and motility on STIM1–Orai1-dependent SOCE. High-resolution microscopy showed only 10% of subplasmalemmal STIM1 clusters to be colocalized with mitochondria. Impairments of mitochondrial Ca2+ handling by inhibition of mitochondrial Na+-Ca2+ exchanger (NCXmito) or depolarization only partially suppressed Ca2+ entry in cells overexpressing STIM1-Orai1. However, SOCE was completely abolished when both NCXmito was inhibited and the inner mitochondrial membrane was depolarized, in STIM1- and Orai1-overexpressing cells. Immobilization of mitochondria by expression of mAKAP-RFP-CAAX, a construct that physically links mitochondria to the plasma membrane, affected the Ca2+ handling of the organelles but not the activity of SOCE. Our observations indicate that mitochondrial Ca2+ uptake, including reversal of NCXmito, is fundamental for STIM1–Orai1-dependent SOCE, whereas the proximity of mitochondria to STIM1-Orai1 SOCE units and their motility is not required.
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Affiliation(s)
- Shamim Naghdi
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Markus Waldeck-Weiermair
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Ismene Fertschai
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Michael Poteser
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Wolfgang F. Graier
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
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42
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43
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Korzeniowski MK, Szanda G, Balla T, Spät A. Store-operated Ca2+ influx and subplasmalemmal mitochondria. Cell Calcium 2009; 46:49-55. [PMID: 19427033 DOI: 10.1016/j.ceca.2009.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Revised: 04/02/2009] [Accepted: 04/06/2009] [Indexed: 12/11/2022]
Abstract
Calcium depletion of the endoplasmic reticulum (ER) induces oligomerisation, puncta formation and translocation of the ER Ca(2+) sensor proteins, STIM1 and -2 into plasma membrane (PM)-adjacent regions of the ER, where they activate the Orai1, -2 or -3 proteins present in the opposing PM. These proteins form ion channels through which store-operated Ca(2+) influx (SOC) occurs. Calcium ions exert negative feed-back on SOC. Here we examined whether subplasmalemmal mitochondria, which reduce this feed-back by Ca(2+) uptake, are located within or out of the high-Ca(2+) microdomains (HCMDs) formed between the ER and plasmalemmal Orai1 channels. For this purpose, COS-7 cells were cotransfected with Orai1, STIM1 labelled with YFP or mRFP and the mitochondrially targeted Ca(2+) sensitive fluorescent protein inverse-Pericam. Depletion of ER Ca(2+) with ATP+thapsigargin (in Ca(2+)-free medium) induced the appearance of STIM1 puncta in the < or =100 nm wide subplasmalemmal space, as examined with TIRF. Mitochondria were located either in the gaps between STIM1-tagged puncta or in remote, STIM1-free regions. After addition of Ca(2+) mitochondrial Ca(2+) concentration increased irrespective of the mitochondrion-STIM1 distance. These observations indicate that mitochondria are exposed to Ca(2+) diffused laterally from the HCMDs formed between the PM and the subplasmalemmal ER.
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Affiliation(s)
- Marek K Korzeniowski
- Section on Molecular Signal Transduction, Program on Developmental Neuroscience, NICHD, NIH, Bethesda, MD, USA
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44
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Demaurex N, Poburko D, Frieden M. Regulation of plasma membrane calcium fluxes by mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1383-94. [PMID: 19161976 DOI: 10.1016/j.bbabio.2008.12.012] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 12/21/2008] [Accepted: 12/29/2008] [Indexed: 11/27/2022]
Abstract
The role of mitochondria in cell signaling is becoming increasingly apparent, to an extent that the signaling role of mitochondria appears to have stolen the spotlight from their primary function as energy producers. In this chapter, we will review the ionic basis of calcium handling by mitochondria and discuss the mechanisms that these organelles use to regulate the activity of plasma membrane calcium channels and transporters.
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Affiliation(s)
- Nicolas Demaurex
- Department of Cell Physiology and Metabolism, University of Geneva, 1, rue Michel-Servet, CH-1211 Geneva 4, Switzerland
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45
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Bird GS, DeHaven WI, Smyth JT, Putney JW. Methods for studying store-operated calcium entry. Methods 2008; 46:204-12. [PMID: 18929662 PMCID: PMC2643845 DOI: 10.1016/j.ymeth.2008.09.009] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Accepted: 09/12/2008] [Indexed: 12/01/2022] Open
Abstract
Activation of surface membrane receptors coupled to phospholipase C results in the generation of cytoplasmic Ca2+ signals comprised of both intracellular Ca2+ release, and enhanced entry of Ca2+ across the plasma membrane. A primary mechanism for this Ca2+ entry process is attributed to store-operated Ca2+ entry, a process that is activated by depletion of Ca2+ ions from an intracellular store by inositol 1,4,5-trisphosphate. Our understanding of the mechanisms underlying both Ca2+ release and store-operated Ca2+ entry have evolved from experimental approaches that include the use of fluorescent Ca2+ indicators and electrophysiological techniques. Pharmacological manipulation of this Ca2+ signaling process has been somewhat limited; but recent identification of key molecular players, STIM and Orai family proteins, has provided new approaches. Here we describe practical methods involving fluorescent Ca2+ indicators and electrophysiological approaches for dissecting the observed intracellular Ca2+ signal to reveal characteristics of store-operated Ca2+ entry, highlighting the advantages, and limitations, of these approaches.
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Affiliation(s)
- Gary S Bird
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, P.O. Box 12233, Research Triangle Park, NC 27709, USA.
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46
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Borges S, Lindstrom S, Walters C, Warrier A, Wilson M. Discrete influx events refill depleted Ca2+ stores in a chick retinal neuron. J Physiol 2007; 586:605-26. [PMID: 18033816 DOI: 10.1113/jphysiol.2007.143339] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The depletion of ER Ca2+ stores, following the release of Ca2+ during intracellular signalling, triggers the Ca2+ entry across the plasma membrane known as store-operated calcium entry (SOCE). We show here that brief, local [Ca2+]i increases (motes) in the thin dendrites of cultured retinal amacrine cells derived from chick embryos represent the Ca2+ entry events of SOCE and are initiated by sphingosine-1-phosphate (S1P), a sphingolipid with multiple cellular signalling roles. Externally applied S1P elicits motes but not through a G protein-coupled membrane receptor. The endogenous precursor to S1P, sphingosine, also elicits motes but its action is suppressed by dimethylsphingosine (DMS), an inhibitor of sphingosine phosphorylation. DMS also suppresses motes induced by store depletion and retards the refilling of depleted stores. These effects are reversed by exogenously applied S1P. In these neurons formation of S1P is a step in the SOCE pathway that promotes Ca2+ entry in the form of motes.
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47
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Parekh AB. Functional consequences of activating store-operated CRAC channels. Cell Calcium 2007; 42:111-21. [PMID: 17445883 DOI: 10.1016/j.ceca.2007.02.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 02/21/2007] [Accepted: 02/21/2007] [Indexed: 11/26/2022]
Abstract
Store-operated CRAC channels, which are activated by the emptying of the endoplasmic reticulum Ca(2+) stores, are an important and widespread route for triggering rises in cytoplasmic Ca(2+). The cellular responses that are activated in response to Ca(2+) entry through CRAC channels are being dissected out, and recent evidence has established that CRAC channels can induce both short-term (safeguarding the Ca(2+) content of the endoplasmic reticulum, maintenance of cytoplasmic Ca(2+) oscillations, enzyme activation, secretion) and long-term (gene expression) changes in cells. CRAC channel activation is therefore capable of evoking a range of temporally distinct responses, highlighting the versatility of this ubiquitous Ca(2+) entry pathway.
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Affiliation(s)
- Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Sherrington Building, Parks Road, Oxford, UK.
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48
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González Narváez AA, Castillo A. Ca2+ store determines gating of store operated calcium entry in mammalian skeletal muscle. J Muscle Res Cell Motil 2007; 28:105-13. [PMID: 17616822 DOI: 10.1007/s10974-007-9105-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Accepted: 04/18/2007] [Indexed: 10/23/2022]
Abstract
This work describes the gating of the store operated calcium entry (SOCE) in adult mammalian skeletal muscle. Flexor digitorum brevis fibers (FDB) were isolated from adult mice and exposed to conditions to deplete the sarcoplasmic reticulum (SR). A transient SR depletion caused either by repetitive depolarizations, chlorocresol (CMC) or, cyclopiazonic acid (CPA) induced a bell shaped calcium entry that raised the [Ca(2+)](i) to a maximum of 27.09 +/- 4.35 nM from the resting value. The activation time to reach 10-90% of the maximum amplitude was 112 +/- 10 s (n = 22). On the other hand, any mechanism that caused a permanent SR depletion (like thapsigargin, continuous CPA, or continuous CMC) triggered a calcium entry pathway that lasted 325 +/- 23 s and raised the [Ca(2+)](i )to 129.50 +/- 13.05 nM from the resting level (n = 28). Then, a prolonged depletion triggered an increase in [Ca(2+)](i) to higher values and for a longer time than when the SR is transiently depleted (p < 0.001). Our results, in skeletal muscle, showed that calcium store depletion was the signal for SOCE activation and how the SR got depleted was not relevant. Also, we found that SOCE deactivation was not caused by [Ca(2+)](i) but by the SR content. Our results suggest that the SR calcium content plays an important role in SOCE gating in mammalian skeletal muscle and a calcium sensor is located inside the SR.
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Affiliation(s)
- Adom A González Narváez
- Laboratorio de Cardiología Molecular, Centro de Biociencia, Fundación Instituto de Estudios Avanzados, Car. Nac. Hoyo de Puerta, Sartenejas, Baruta, Caracas 1080, Venezuela.
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Lis A, Peinelt C, Beck A, Parvez S, Monteilh-Zoller M, Fleig A, Penner R. CRACM1, CRACM2, and CRACM3 are store-operated Ca2+ channels with distinct functional properties. Curr Biol 2007; 17:794-800. [PMID: 17442569 PMCID: PMC5663639 DOI: 10.1016/j.cub.2007.03.065] [Citation(s) in RCA: 305] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 03/27/2007] [Accepted: 03/28/2007] [Indexed: 02/01/2023]
Abstract
STIM1 in the endoplasmic reticulum and CRACM1 in the plasma membrane are essential molecular components for controlling the store-operated CRAC current. CRACM1 proteins multimerize and bind STIM1, and the combined overexpression of STIM1 and CRACM1 reconstitutes amplified CRAC currents. Mutations in CRACM1 determine the selectivity of CRAC currents, demonstrating that CRACM1 forms the CRAC channel's ion-selective pore, but the CRACM1 homologs CRACM2 and CRACM3 are less well characterized. Here, we show that both CRACM2 and CRACM3, when overexpressed in HEK293 cells stably expressing STIM1, potentiate I(CRAC) to current amplitudes 15-20 times larger than native I(CRAC). A nonconducting mutation of CRACM1 (E106Q) acts as a dominant negative for all three CRACM homologs, suggesting that they can form heteromultimeric channel complexes. All three CRACM homologs exhibit distinct properties in terms of selectivity for Ca(2+) and Na(+), differential pharmacological effects in response to 2-APB, and strikingly different feedback regulation by intracellular Ca(2+). Each of the CRAC channel proteins' specific functional features and the potential heteromerization provide for flexibility in shaping Ca(2+) signals, and their characteristic biophysical and pharmacological properties will aid in identifying CRAC-channel species in native cells that express them.
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Affiliation(s)
- Annette Lis
- Center for Biomedical Research The Queen’s Medical Center Honolulu, Hawaii 96813
- John A. Burns School of Medicine University of Hawaii, Honolulu, Hawaii 96813
| | - Christine Peinelt
- Center for Biomedical Research The Queen’s Medical Center Honolulu, Hawaii 96813
- John A. Burns School of Medicine University of Hawaii, Honolulu, Hawaii 96813
| | - Andreas Beck
- Center for Biomedical Research The Queen’s Medical Center Honolulu, Hawaii 96813
- John A. Burns School of Medicine University of Hawaii, Honolulu, Hawaii 96813
| | - Suhel Parvez
- Center for Biomedical Research The Queen’s Medical Center Honolulu, Hawaii 96813
- John A. Burns School of Medicine University of Hawaii, Honolulu, Hawaii 96813
| | - Mahealani Monteilh-Zoller
- Center for Biomedical Research The Queen’s Medical Center Honolulu, Hawaii 96813
- John A. Burns School of Medicine University of Hawaii, Honolulu, Hawaii 96813
| | - Andrea Fleig
- Center for Biomedical Research The Queen’s Medical Center Honolulu, Hawaii 96813
- John A. Burns School of Medicine University of Hawaii, Honolulu, Hawaii 96813
| | - Reinhold Penner
- Center for Biomedical Research The Queen’s Medical Center Honolulu, Hawaii 96813
- John A. Burns School of Medicine University of Hawaii, Honolulu, Hawaii 96813
- Correspondence:
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Trenker M, Malli R, Fertschai I, Levak-Frank S, Graier WF. Uncoupling proteins 2 and 3 are fundamental for mitochondrial Ca2+ uniport. Nat Cell Biol 2007; 9:445-452. [PMID: 17351641 PMCID: PMC4060164 DOI: 10.1038/ncb1556] [Citation(s) in RCA: 277] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Accepted: 01/17/2007] [Indexed: 01/05/2023]
Abstract
Mitochondrial Ca(2+) uptake is crucial for the regulation of the rate of oxidative phosphorylation, the modulation of spatio-temporal cytosolic Ca(2+) signals and apoptosis. Although the phenomenon of mitochondrial Ca(2+) sequestration, its characteristics and physiological consequences have been convincingly reported, the actual protein(s) involved in this process are unknown. Here, we show that the uncoupling proteins 2 and 3 (UCP2 and UCP3) are essential for mitochondrial Ca(2+) uptake. Using overexpression, knockdown (small interfering RNA) and mutagenesis experiments, we demonstrate that UCP2 and UCP3 are elementary for mitochondrial Ca(2+) sequestration in response to cell stimulation under physiological conditions - observations supported by isolated liver mitochondria of Ucp2(-/-) mice lacking ruthenium red-sensitive Ca(2+) uptake. Our results reveal a novel molecular function for UCP2 and UCP3, and may provide the molecular mechanism for their reported effects. Moreover, the identification of proteins fundemental for mitochondrial Ca(2+) uptake expands our knowledge of the physiological role for mitochondrial Ca(2+) sequestration.
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Affiliation(s)
- Michael Trenker
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Ismene Fertschai
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Sanja Levak-Frank
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Wolfgang F. Graier
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
- Correspondence should be addressed to W.F.G. ()
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