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Humer C, Romanin C, Höglinger C. Highlighting the Multifaceted Role of Orai1 N-Terminal- and Loop Regions for Proper CRAC Channel Functions. Cells 2022; 11:371. [PMID: 35159181 PMCID: PMC8834118 DOI: 10.3390/cells11030371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/14/2022] [Accepted: 01/15/2022] [Indexed: 11/16/2022] Open
Abstract
Orai1, the Ca2+-selective pore in the plasma membrane, is one of the key components of the Ca2+release-activated Ca2+ (CRAC) channel complex. Activated by the Ca2+ sensor in the endoplasmic reticulum (ER) membrane, stromal interaction molecule 1 (STIM1), via direct interaction when ER luminal Ca2+ levels recede, Orai1 helps to maintain Ca2+ homeostasis within a cell. It has already been proven that the C-terminus of Orai1 is indispensable for channel activation. However, there is strong evidence that for CRAC channels to function properly and maintain all typical hallmarks, such as selectivity and reversal potential, additional parts of Orai1 are needed. In this review, we focus on these sites apart from the C-terminus; namely, the second loop and N-terminus of Orai1 and on their multifaceted role in the functioning of CRAC channels.
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Affiliation(s)
| | | | - Carmen Höglinger
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria; (C.H.); (C.R.)
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2
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Abstract
Cell survival and normal cell function require a highly coordinated and precise regulation of basal cytosolic Ca2+ concentrations. The primary source of Ca2+ entry into the cell is mediated by the Ca2+ release-activated Ca2+ (CRAC) channel. Its action is stimulated in response to internal Ca2+ store depletion. The fundamental constituents of CRAC channels are the Ca2+ sensor, stromal interaction molecule 1 (STIM1) anchored in the endoplasmic reticulum, and a highly Ca2+-selective pore-forming subunit Orai1 in the plasma membrane. The precise nature of the Orai1 pore opening is currently a topic of intensive research. This review describes how Orai1 gating checkpoints in the middle and cytosolic extended transmembrane regions act together in a concerted manner to ensure an opening-permissive Orai1 channel conformation. In this context, we highlight the effects of the currently known multitude of Orai1 mutations, which led to the identification of a series of gating checkpoints and the determination of their role in diverse steps of the Orai1 activation cascade. The synergistic action of these gating checkpoints maintains an intact pore geometry, settles STIM1 coupling, and governs pore opening. We describe the current knowledge on Orai1 channel gating mechanisms and summarize still open questions of the STIM1-Orai1 machinery.
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3
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Abstract
Ca2+ release activated Ca2+ (CRAC) channels represent a primary pathway for Ca2+ to enter non-excitable cells. The two key players in this process are the stromal interaction molecule (STIM), a Ca2+ sensor embedded in the membrane of the endoplasmic reticulum, and Orai, a highly Ca2+ selective ion channel located in the plasma membrane. Upon depletion of the internal Ca2+ stores, STIM is activated, oligomerizes, couples to and activates Orai. This review provides an overview of novel findings about the CRAC channel activation mechanisms, structure and gating. In addition, it highlights, among diverse STIM and Orai mutants, also the disease-related mutants and their implications.
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Affiliation(s)
- Carmen Butorac
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria
| | - Adéla Krizova
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria.
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4
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Krizova A, Maltan L, Derler I. Critical parameters maintaining authentic CRAC channel hallmarks. Eur Biophys J 2019; 48:425-445. [PMID: 30903264 PMCID: PMC6647248 DOI: 10.1007/s00249-019-01355-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/20/2018] [Accepted: 03/06/2019] [Indexed: 12/20/2022]
Abstract
Ca2+ ions represent versatile second messengers that regulate a huge diversity of processes throughout the cell's life. One prominent Ca2+ entry pathway into the cell is the Ca2+ release-activated Ca2+ (CRAC) ion channel. It is fully reconstituted by the two molecular key players: the stromal interaction molecule (STIM1) and Orai. STIM1 is a Ca2+ sensor located in the membrane of the endoplasmic reticulum, and Orai, a highly Ca2+ selective ion channel embedded in the plasma membrane. Ca2+ store-depletion leads initially to the activation of STIM1 which subsequently activates Orai channels via direct binding. Authentic CRAC channel hallmarks and biophysical characteristics include high Ca2+ selectivity with a reversal potential in the range of + 50 mV, small unitary conductance, fast Ca2+-dependent inactivation and enhancements in currents upon the switch from a Na+-containing divalent-free to a Ca2+-containing solution. This review provides an overview on the critical determinants and structures within the STIM1 and Orai proteins that establish these prominent CRAC channel characteristics.
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Affiliation(s)
- Adéla Krizova
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Lena Maltan
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020, Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020, Linz, Austria.
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5
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Zang J, Zuo D, Shogren KL, Gustafson CT, Zhou Z, Thompson MA, Guo R, Prakash YS, Lu L, Guo W, Maran A, Yaszemski MJ. STIM1 expression is associated with osteosarcoma cell survival. Chin J Cancer Res 2019; 31:203-211. [PMID: 30996578 PMCID: PMC6433589 DOI: 10.21147/j.issn.1000-9604.2019.01.15] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Objective To examine the role of store-operated calcium entry (SOCE) and stromal interaction molecule 1 (STIM1) in survival and migration of osteosarcoma cells and investigate what blockade of store-operated Ca2+ contributes to the regulation of osteosarcoma cells.
Methods First, we examined the expression levels of STIM1 in osteosarcoma cell lines by Western analysis and in tissue specimens by immunohistochemistry. Second, we investigated the effect of SOCE and STIM1 on osteosarcoma cell viability using MTS assays and on cell proliferation using colony formation. Third, we investigated the role of SOCE and STIM1 in cell migration using wound healing assays and Boyden chamber assays. Finally, we studied the effect of SOCE on the nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) activity by luciferase assays. Results STIM1 was overexpressed in osteosarcoma cell lines and tissue specimens and was associated with poor survival of osteosarcoma patients. Also, inhibition of SOCE and STIM1 decreased the cell viability and migration of osteosarcoma cells. Furthermore, our results showed that blockade of store-operated Ca2+ channels involved down-regulation of NFATc1 in osteosarcoma cells.
Conclusions STIM1 is essential for osteosarcoma cell functions, and STIM1 and Ca2+ entry pathway could be further explored as molecular targets in the treatment of osteosarcoma.
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Affiliation(s)
- Jie Zang
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA.,Musculoskeletal Tumor Center, Peking University People's Hospital, Beijing 100044, China
| | - Dongqing Zuo
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA.,Department of Orthopaedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China
| | - Kristen L Shogren
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA
| | - Carl T Gustafson
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA
| | - Zifei Zhou
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Ruiwei Guo
- Department of Cardiology, Kunming General Hospital of Chengdu Military Command of PLA, Kunming 650032, China
| | - Y S Prakash
- Department of Orthopaedics, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Lichun Lu
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Wei Guo
- Musculoskeletal Tumor Center, Peking University People's Hospital, Beijing 100044, China
| | - Avudaiappan Maran
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Michael J Yaszemski
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
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6
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Abstract
A primary calcium (Ca2+) entry pathway into non-excitable cells is through the store-operated Ca2+ release activated Ca2+ (CRAC) channel. Ca2+ entry into cells is responsible for the initiation of diverse signalling cascades that affect essential cellular processes like gene regulation, cell growth and death, secretion and gene transcription. Upon depletion of intracellular Ca2+ stores within the endoplasmic reticulum (ER), the CRAC channel opens to refill depleted stores. The two key limiting molecular players of the CRAC channel are the stromal interaction molecule (STIM1) embedded in the ER-membrane and Orai1, residing in the plasma membrane (PM), respectively. Together, they form a highly Ca2+ selective ion channel complex. STIM1 senses the Ca2+ content of the ER and confers Ca2+ store-depletion into the opening of Orai1 channels in the PM for triggering Ca2+-dependent gene transcription, T-cell activation or mast cell degranulation. The interplay of Orai and STIM proteins in the CRAC channel signalling cascade has been the main focus of research for more than twelve years. This chapter focuses on current knowledge and main experimental advances in the understanding of Orai1 activation by STIM1, thereby portraying key mechanistic steps in the CRAC channel signalling cascade.
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Affiliation(s)
- Victoria Lunz
- Institute of Biophysics, Johannes Kepler University Linz, A-4020, Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, A-4020, Linz, Austria.
| | - Irene Frischauf
- Institute of Biophysics, Johannes Kepler University Linz, A-4020, Linz, Austria.
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7
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Woo J, Kim HJ, Nam YR, Kim YK, Lee EJ, Choi I, Kim SJ, Lee W, Nam JH. Mitochondrial dysfunction reduces the activity of KIR2.1 K + channel in myoblasts via impaired oxidative phosphorylation. Korean J Physiol Pharmacol 2018; 22:697-703. [PMID: 30402030 PMCID: PMC6205933 DOI: 10.4196/kjpp.2018.22.6.697] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 08/28/2018] [Accepted: 08/29/2018] [Indexed: 11/15/2022]
Abstract
Myoblast fusion depends on mitochondrial integrity and intracellular Ca2+ signaling regulated by various ion channels. In this study, we investigated the ionic currents associated with [Ca2+]i regulation in normal and mitochondrial DNA-depleted (ρ0) L6 myoblasts. The ρ0 myoblasts showed impaired myotube formation. The inwardly rectifying K+ current (IKir) was largely decreased with reduced expression of KIR2.1, whereas the voltage-operated Ca2+ channel and Ca2+-activated K+ channel currents were intact. Sustained inhibition of mitochondrial electron transport by antimycin A treatment (24 h) also decreased the IKir. The ρ0 myoblasts showed depolarized resting membrane potential and higher basal [Ca2+]i. Our results demonstrated the specific downregulation of IKir by dysfunctional mitochondria. The resultant depolarization and altered Ca2+ signaling might be associated with impaired myoblast fusion in ρ0 myoblasts.
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Affiliation(s)
- JooHan Woo
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Hyun Jong Kim
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Korea.,Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Korea
| | - Yu Ran Nam
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Korea.,Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Korea
| | - Yung Kyu Kim
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Korea
| | - Eun Ju Lee
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan 38541, Korea
| | - Inho Choi
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan 38541, Korea
| | - Sung Joon Kim
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Wan Lee
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Korea.,Department of Biochemistry, Dongguk University College of Medicine, Gyeongju 38066, Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Korea.,Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Korea
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8
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Tam KC, Ali E, Hua J, Chataway T, Barritt GJ. Evidence for the interaction of peroxiredoxin-4 with the store-operated calcium channel activator STIM1 in liver cells. Cell Calcium 2018; 74:14-28. [PMID: 29804005 DOI: 10.1016/j.ceca.2018.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Revised: 05/04/2018] [Accepted: 05/12/2018] [Indexed: 12/22/2022]
Abstract
Ca2+ entry through store-operated Ca2+ channels (SOCs) in the plasma membrane (PM) of hepatocytes plays a central role in the hormonal regulation of liver metabolism. SOCs are composed of Orai1, the channel pore protein, and STIM1, the activator protein, and are regulated by hormones and reactive oxygen species (ROS). In addition to Orai1, STIM1 also interacts with several other intracellular proteins. Most previous studies of the cellular functions of Orai1 and STIM1 have employed immortalised cells in culture expressing ectopic proteins tagged with a fluorescent polypeptide such as GFP. Little is known about the intracellular distributions of endogenous Orai1 and STIM1. The aims are to determine the intracellular distribution of endogenous Orai1 and STIM1 in hepatocytes and to identify novel STIM1 binding proteins. Subcellular fractions of rat liver were prepared by homogenisation and differential centrifugation. Orai1 and STIM1 were identified and quantified by western blot. Orai1 was found in the PM (0.03%), heavy (44%) and light (27%) microsomal fractions, and STIM1 in the PM (0.09%), and heavy (85%) and light (13%) microsomal fractions. Immunoprecipitation of STIM1 followed by LC/MS or western blot identified peroxiredoxin-4 (Prx-4) as a potential STIM1 binding protein. Prx-4 was found principally in the heavy microsomal fraction. Knockdown of Prx-4 using siRNA, or inhibition of Prx-4 using conoidin A, did not affect Ca2+ entry through SOCs but rendered SOCs susceptible to inhibition by H2O2. It is concluded that, in hepatocytes, a considerable proportion of endogenous Orai1 and STIM1 is located in the rough ER. In the rough ER, STIM1 interacts with Prx-4, and this interaction may contribute to the regulation by ROS of STIM1 and SOCs.
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Affiliation(s)
- Ka Cheung Tam
- Discipline of Medical Biochemistry, College of Medicine and Public Health, Flinders University, Adelaide, South Australia, 5001, Australia
| | - Eunus Ali
- Discipline of Medical Biochemistry, College of Medicine and Public Health, Flinders University, Adelaide, South Australia, 5001, Australia
| | - Jin Hua
- Discipline of Medical Biochemistry, College of Medicine and Public Health, Flinders University, Adelaide, South Australia, 5001, Australia
| | - Tim Chataway
- Discipline of Medical Biochemistry, College of Medicine and Public Health, Flinders University, Adelaide, South Australia, 5001, Australia
| | - Greg J Barritt
- Discipline of Medical Biochemistry, College of Medicine and Public Health, Flinders University, Adelaide, South Australia, 5001, Australia.
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9
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López E, Gómez-Gordo L, Cantonero C, Bermejo N, Pérez-Gómez J, Granados MP, Salido GM, Rosado Dionisio JA, Redondo Liberal PC. Stanniocalcin 2 Regulates Non-capacitative Ca 2+ Entry and Aggregation in Mouse Platelets. Front Physiol 2018; 9:266. [PMID: 29628897 PMCID: PMC5876523 DOI: 10.3389/fphys.2018.00266] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 03/08/2018] [Indexed: 12/11/2022] Open
Abstract
Stanniocalcin 2 (STC2) is a fish protein that controls body Ca2+ and phosphate metabolism. STC2 has also been described in mammals, and as platelet function highly depends on both extracellular and intracellular Ca2+, we have explored its expression and function in these cells. STC2−/− mice exhibit shorter tail bleeding time than WT mice. Platelets from STC2-deficient mice showed enhanced aggregation, as well as enhanced Ca2+ mobilization in response to the physiological agonist thrombin (Thr) and the diacylglycerol analog, OAG, a selective activator of the non-capacitative Ca2+ entry channels. Interestingly, platelets from STC2−/− mice exhibit attenuated interaction between STIM1 and Orai1 in response to Thr, thus suggesting that STC2 is required for Thr-evoked STIM1-Orai1 interaction and the subsequent store-operated Ca2+ entry (SOCE). We have further assessed possible changes in the expression of the most relevant channels involved in non-capacitative Ca2+ entry in platelets. Then, protein expression of Orai3, TRPC3 and TRPC6 were evaluated by Western blotting, and the results revealed that while the expression of Orai3 was enhanced in the STC2-deficient mice, others like TRPC3 and TRPC6 remains almost unaltered. Summarizing, our results provide for the first time evidence for a role of STC2 in platelet physiology through the regulation of agonist-induced Ca2+ entry, which might be mediated by the regulation of Orai3 channel expression.
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Affiliation(s)
- Esther López
- Department of Physiology (PHYCELL) of the Veterinary Faculty, University of Extremadura, Cáceres, Spain
| | - L Gómez-Gordo
- Department of Animal Medicine, Veterinary Faculty University of Extremadura, Cáceres, Spain
| | - Carlos Cantonero
- Department of Physiology (PHYCELL) of the Veterinary Faculty, University of Extremadura, Cáceres, Spain
| | - Nuria Bermejo
- Hematology Unit, San Pedro de Alcantara Hospital, Cáceres, Spain
| | - Jorge Pérez-Gómez
- Faculty of Sport Sciences, University of Extremadura, Cáceres, Spain
| | - María P Granados
- Aldea Moret Health Center, Extremadura Health Service, Cáceres, Spain
| | - Gines M Salido
- Institute of Molecular Pathology Biomarkers, Cáceres, Spain
| | - Juan A Rosado Dionisio
- Department of Physiology (PHYCELL) of the Veterinary Faculty, University of Extremadura, Cáceres, Spain
| | - Pedro C Redondo Liberal
- Department of Physiology (PHYCELL) of the Veterinary Faculty, University of Extremadura, Cáceres, Spain
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10
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Abstract
Fast Ca2+-dependent inactivation (FCDI) is a safety mechanism limiting Ca2+ entry through some types of Ca2+ channels, including Ca2+ release-activated Ca2+ (CRAC) channels. This type of inactivation is caused by Ca2+, which passes through Ca2+ channel and binds to a specific site within a short distance from the inner mouth of the pore, causing channel to shut.The main technique that is used to investigate FCDI is whole-cell patch clamping. Since the cloning of the molecular components of the CRAC channel, STIM1 and Orai1, FCDI of CRAC channel has been studied using HEK293T heterologous expression system. In this paper we describe a method of quantifying CRAC channel FCDI by using instantaneous tail currents.
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Affiliation(s)
- Grigori Y Rychkov
- School of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia.
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11
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Jardín I, Albarran L, Salido GM, López JJ, Sage SO, Rosado JA. Fine-tuning of store-operated calcium entry by fast and slow Ca 2+-dependent inactivation: Involvement of SARAF. Biochim Biophys Acta Mol Cell Res 2018; 1865:463-9. [PMID: 29223474 DOI: 10.1016/j.bbamcr.2017.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [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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12
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Abstract
A primary Ca2+ entry pathway in non-excitable cells is established by the Ca2+ release-activated Ca2+ channels. Their two limiting molecular components include the Ca2+-sensor protein STIM1 located in the endoplasmic reticulum and the Orai channel in the plasma membrane. STIM1 senses the luminal Ca2+ content, and store depletion induces its oligomerization into puncta-like structures, thereby triggering coupling to as well as activation of Orai channels. A C-terminal STIM1 domain is assumed to couple to both C- and N-terminal, cytosolic strands of Orai, accomplishing gating of the channel. Here we highlight the inter- and intramolecular steps of the STIM1-Orai signaling cascade together with critical sites of the pore structure that accomplishes Ca2+ permeation.
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Affiliation(s)
- Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria.
| | - Rainer Schindl
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, 4020, Linz, Austria.
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13
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Ali ES, Rychkov GY, Barritt GJ. Metabolic Disorders and Cancer: Hepatocyte Store-Operated Ca2+ Channels in Nonalcoholic Fatty Liver Disease. Store-Operated Ca²⁺ Entry (SOCE) Pathways 2017. [DOI: 10.1007/978-3-319-57732-6_30] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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14
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Abstract
Ca2+ entry into the cell via store-operated Ca2+ release-activated Ca2+ (CRAC) channels triggers diverse signaling cascades that affect cellular processes like cell growth, gene regulation, secretion, and cell death. These store-operated Ca2+ channels open after depletion of intracellular Ca2+ stores, and their main features are fully reconstituted by the two molecular key players: the stromal interaction molecule (STIM) and Orai. STIM represents an endoplasmic reticulum-located Ca2+ sensor, while Orai forms a highly Ca2+-selective ion channel in the plasma membrane. Functional as well as mutagenesis studies together with structural insights about STIM and Orai proteins provide a molecular picture of the interplay of these two key players in the CRAC signaling cascade. This review focuses on the main experimental advances in the understanding of the STIM1-Orai choreography, thereby establishing a portrait of key mechanistic steps in the CRAC channel signaling cascade. The focus is on the activation of the STIM proteins, the subsequent coupling of STIM1 to Orai1, and the consequent structural rearrangements that gate the Orai channels into the open state to allow Ca2+ permeation into the cell.
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Affiliation(s)
- Isabella Derler
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria; and
| | - Isaac Jardin
- Department of Physiology, University of Extremadura, Cáceres, Spain
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria; and
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15
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Abstract
Store-operated Ca(2+) entry (SOCE) is an important mechanism for Ca(2+) influx in non-excitable cells, also present in excitable cells. The activation of store-operated channels (SOCs) is finely regulated by the filling state of the intracellular agonist-sensitive Ca(2+) compartments, and both, the mechanism of sensing the Ca(2+) stores and the nature and functional properties of the SOCs, have been a matter of intense investigation and debate. The identification of STIM1 as the endoplasmic reticulum Ca(2+) sensor and both Orai1, as the pore-forming subunit of the channels mediating the Ca(2+)-selective store-operated current, and the members of the TRPC subfamily of proteins, as the channels mediating the cation-permeable SOCs, has shed new light on the underlying events. This review summarizes the initial hypothesis and the current advances on the mechanism of activation of SOCE.
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Affiliation(s)
- Pedro C Redondo
- Department of Physiology, University of Extremadura, Cáceres, Spain
| | - Juan A Rosado
- Department of Physiology, University of Extremadura, Cáceres, Spain
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