601
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Takahashi Y, Watanabe H, Murakami M, Ono K, Munehisa Y, Koyama T, Nobori K, Iijima T, Ito H. Functional role of stromal interaction molecule 1 (STIM1) in vascular smooth muscle cells. Biochem Biophys Res Commun 2007; 361:934-40. [PMID: 17689489 DOI: 10.1016/j.bbrc.2007.07.096] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Accepted: 07/18/2007] [Indexed: 02/01/2023]
Abstract
We investigated the functional role of STIM1, a Ca(2+) sensor in the endoplasmic reticulum (ER) that regulates store-operated Ca(2+) entry (SOCE), in vascular smooth muscle cells (VSMCs). STIM1 was mainly localized at the ER and plasma membrane. The knockdown of STIM1 expression by small interfering (si) RNA drastically decreased SOCE. In contrast, an EF-hand mutant of STIM1, STIM1(E87A), produced a marked increase in SOCE, which was abolished by co-transfection with siRNA to transient receptor potential canonical 1 (TRPC1). In addition, transfection with siRNA against STIM1 suppressed phosphorylation of cAMP-responsive element binding protein (CREB) and cell growth. These results suggest that STIM1 is an essential component of SOCE and that it is involved in VSMC proliferation.
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Affiliation(s)
- Yoichiro Takahashi
- Second Department of Internal Medicine, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan
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602
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Cai X. Molecular evolution and functional divergence of the Ca(2+) sensor protein in store-operated Ca(2+) entry: stromal interaction molecule. PLoS One 2007; 2:e609. [PMID: 17622354 PMCID: PMC1904252 DOI: 10.1371/journal.pone.0000609] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Accepted: 06/13/2007] [Indexed: 01/06/2023] Open
Abstract
Receptor-mediated Ca2+ signaling in many non-excitable cells initially induces Ca2+ release from intracellular Ca2+ stores, followed by Ca2+ influx across the plasma membrane. Recent findings have suggested that stromal interaction molecules (STIMs) function as the Ca2+ sensor to detect changes of Ca2+ content in the intracellular Ca2+ stores. Human STIMs and invertebrate STIM share several functionally important protein domains, but diverge significantly in the C-terminus. To better understand the evolutionary significance of STIM activity, phylogenetic analysis of the STIM protein family was conducted after extensive database searching. Results from phylogeny and sequence analysis revealed early adaptation of the C-terminal divergent domains in Urochordata, before the expansion of STIMs in Vertebrata. STIMs were subsequently subjected to one round of gene duplication as early as in the Euteleostomi lineage in vertebrates, with a second round of fish-specific gene duplication. After duplication, STIM-1 and STIM-2 molecules appeared to have undergone purifying selection indicating strong evolutionary constraints within each group. Furthermore, sequence analysis of the EF-hand Ca2+ binding domain and the SAM domain, together with functional divergence studies, identified critical regions/residues likely underlying functional changes, and provided evidence for the hypothesis that STIM-1 and STIM-2 might have developed distinct functional properties after duplication.
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Affiliation(s)
- Xinjiang Cai
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America.
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603
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Mueller P, Quintana A, Griesemer D, Hoth M, Pieters J. Disruption of the cortical actin cytoskeleton does not affect store operated Ca2+ channels in human T-cells. FEBS Lett 2007; 581:3557-62. [PMID: 17624329 DOI: 10.1016/j.febslet.2007.06.068] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Revised: 06/24/2007] [Accepted: 06/25/2007] [Indexed: 11/17/2022]
Abstract
Lymphocyte signaling and activation leads to the influx of extracellular Ca(2+) via the activation of Ca(2+) release activated Ca(2+) (CRAC) channels in the plasma membrane. Activation of CRAC channels occurs following emptying of the endoplasmic reticulum intracellular Ca(2+) stores. One model to explain the coupling of store-emptying to CRAC activation is the secretion-like conformational coupling model. This model proposes that store depletion increases junctions between the endoplasmic reticulum and the plasma membrane in a manner that could be regulated by the cortical actin cytoskeleton. Here, we show that stabilization or depolymerization of the actin cytoskeleton failed to affect CRAC activation. We therefore conclude that rearrangement of the actin cytoskeleton is dispensable for store-operated Ca(2+) entry in T-cells.
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Affiliation(s)
- Philipp Mueller
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH 4056 Basel, Switzerland
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604
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Hewavitharana T, Deng X, Soboloff J, Gill DL. Role of STIM and Orai proteins in the store-operated calcium signaling pathway. Cell Calcium 2007; 42:173-82. [PMID: 17602740 DOI: 10.1016/j.ceca.2007.03.009] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 03/22/2007] [Accepted: 03/23/2007] [Indexed: 02/04/2023]
Abstract
Ca(2+) signals are universal among cells in regulating a spectrum of cellular responses. Phospholipase C-coupled receptors activate two components of Ca(2+) signals--rapid Ca(2+) release from ER stores, followed by slower Ca(2+) entry from outside the cell. The coupling process between ER and PM to mediate this "store-operated" Ca(2+) entry process remained until recently a molecular mystery. The recent discovery of the necessity for STIM1 and Orai proteins in this process has provided crucial information on the coupling mechanism between stores and PM Ca(2+) entry. STIM1 is a single spanning membrane protein with an unpaired Ca(2+) binding EF-hand and appears to function as the sensor of ER luminal Ca(2+), and, through redistribution in the ER, transduces information directly to the PM. Orai1 is a tetra-spanning PM protein and functions as the highly Ca(2+)-selective channel in the PM that is gated through interactions with the store-activated ER Ca(2+) sensor. Recent evidence shows the two proteins together are necessary and sufficient for the function of store-operated Ca(2+) entry. However, many questions arise about how and where the interactions of the STIM1 and Orai1 proteins occur within cells. Here we discuss recent information and ideas about the coupling between these proteins that leads to store-operated channel activation.
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Affiliation(s)
- Thamara Hewavitharana
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, MD 21201, United States
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605
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Gwack Y, Feske S, Srikanth S, Hogan PG, Rao A. Signalling to transcription: store-operated Ca2+ entry and NFAT activation in lymphocytes. Cell Calcium 2007; 42:145-56. [PMID: 17572487 DOI: 10.1016/j.ceca.2007.03.007] [Citation(s) in RCA: 243] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2007] [Revised: 03/20/2007] [Accepted: 03/21/2007] [Indexed: 02/04/2023]
Abstract
In cells of the immune system that are stimulated by antigen or antigen-antibody complexes, Ca(2+) entry from the extracellular medium is driven by depletion of endoplasmic reticulum Ca(2+) stores and occurs through specialized store-operated Ca(2+) channels known as Ca(2+)-release-activated Ca(2+) (CRAC) channels. The process of store-operated Ca(2+) influx is essential for short-term as well as long-term responses by immune-system cells. Short-term responses include mast cell degranulation and killing of target cells by effector cytolytic T cells, whereas long-term responses typically involve changes in gene transcription and include T and B cell proliferation and differentiation. Transcription downstream of Ca(2+) influx is in large part funneled through the transcription factor nuclear factor of activated T cells (NFAT), a heavily phosphorylated protein that is cytoplasmic in resting cells, but that enters the nucleus when dephosphorylated by the calmodulin-dependent serine/threonine phosphatase calcineurin. The importance of the Ca(2+)/calcineurin/NFAT signalling pathway for lymphocyte activation is underscored by the finding that the underlying defect in a family with a hereditary severe combined immune deficiency (SCID) syndrome is a defect in CRAC channel function, store-operated Ca(2+) entry, NFAT activation and transcription of cytokines, chemokines and many other NFAT target genes whose transcription is essential for productive immune defence. We recently used a two-pronged genetic approach to identify Orai1 as the pore subunit of the CRAC channel. On the one hand, we initiated a positional cloning approach in which we utilised genome-wide single nucleotide polymorphism (SNP) mapping to identify the genomic region linked to the mutant gene in the SCID family described above. In parallel, we used a genome-wide RNAi screen in Drosophila to identify critical regulators of NFAT nuclear translocation and store-operated Ca(2+) entry. These approaches, together with subsequent mutational and electrophysiological analyses, converged to identify human Orai1 as a pore subunit of the CRAC channel and as the gene product mutated in the SCID patients.
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Affiliation(s)
- Yousang Gwack
- Department of Pathology, Harvard Medical School, The CBR Institute for Biomedical Research, 200 Longwood Avenue, Boston, MA 02115, USA
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606
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Launikonis BS, Ríos E. Store-operated Ca2+ entry during intracellular Ca2+ release in mammalian skeletal muscle. J Physiol 2007; 583:81-97. [PMID: 17569733 PMCID: PMC2277221 DOI: 10.1113/jphysiol.2007.135046] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Store-operated Ca2+ entry (SOCE) is activated following the depletion of internal Ca2+ stores in virtually all eukaryotic cells. Shifted excitation and emission ratioing of fluorescence (SEER) was used to image mag-indo-1 trapped in the tubular (t) system of mechanically skinned rat skeletal muscle fibres to measure SOCE during intracellular Ca2+ release. Cytosolic Ca2+ transients were simultaneously imaged using the fluorescence of rhod-2. Spatially and temporally resolved images of t system [Ca2+] ([Ca2+]t-sys) allowed estimation of Ca2+ entry flux from the rate of decay of [Ca2+]t-sys. Ca2+ release was induced pharmacologically to activate SOCE without voltage-dependent contributions to Ca2+ flux. Inward Ca2+ flux was monotonically dependent on the [Ca2+] gradient, and strongly dependent on the transmembrane potential. The activation of SOCE was controlled locally. It could occur without full Ca2+ store depletion and in less than a second after initiation of store depletion. These results indicate that the molecular agonists of SOCE must be evenly distributed throughout the junctional membranes and can activate rapidly. Termination of SOCE required a net increase in [Ca2+]SR. Activation and termination of SOCE are also demonstrated, for the first time, during a single event of Ca2+ release. At the physiological [Ca2+]t-sys, near 2 mM (relative to t system volume), SOCE flux relative to accessible cytoplasmic volume was at least 18.6 microM s(-1), consistent with times of SR refilling of 1-2 min measured in intact muscle fibres.
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Affiliation(s)
- Bradley S Launikonis
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL 60612, USA.
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607
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Abstract
The mechanisms of agonist-induced calcium entry (ACE) following depletion of intracellular calcium stores have not been fully established. We report here that calcium-independent phospholipase A (iPLA2) is required for robust Ca2+ entry in HaCaT keratinocytes following ATP or UTP stimulation. Lysophosphatidic acid (LPA), an unrelated agonist, evoked Ca2+ release without inducing robust Ca2+ entry. Both LPA and UTP induced the redistribution of STIM1 into puncta which localized to regions near or at the plasma membrane, as well as within the cytoplasm. Plasma membrane-associated STIM1 remained high for up to 10 min after UTP stimulation, whereas it had returned almost to baseline by that time point in LPA-stimulated cells. This correlated with faster reloading of the endoplasmic reticulum Ca2+ stores in LPA treated cells. Thus by differentially regulating store-refilling after agonist-mediated depletion, LPA and UTP may exert distinct effects on the duration of STIM1 localization at the plasma membrane, and thus, on the magnitude and duration of ACE.
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Affiliation(s)
- Kehinde Ross
- Dermatological Sciences, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.
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608
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Gwack Y, Srikanth S, Feske S, Cruz-Guilloty F, Oh-hora M, Neems DS, Hogan PG, Rao A. Biochemical and Functional Characterization of Orai Proteins. J Biol Chem 2007; 282:16232-43. [PMID: 17293345 DOI: 10.1074/jbc.m609630200] [Citation(s) in RCA: 301] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stimulation of immune cells triggers Ca2+ entry through store-operated Ca2+ release-activated Ca2+ channels, promoting nuclear translocation of the transcription factor NFAT. Through genome-wide RNA interference screens in Drosophila, we and others identified olf186-F (Drosophila Orai, dOrai) and dStim as critical components of store-operated Ca2+ entry and showed that dOrai and its human homologue Orai1 are pore subunits of the Ca2+ release-activated Ca2+ channel. Here we report that Orai1 is predominantly responsible for store-operated Ca2+ influx in human embryonic kidney 293 cells and human T cells and fibroblasts, although its paralogue Orai3 can partly compensate in the absence of functional Orai1. All three mammalian Orai are widely expressed at the mRNA level, and all three are incorporated into the plasma membrane. In human embryonic kidney 293 cells, Orai1 is glycosylated at an asparagine residue in the predicted second extracellular loop, but mutation of the residue does not compromise function. STIM1 and Orai1 colocalize after store depletion, but Orai1 does not associate detectably with STIM1 in glycerol gradient centrifugation or coimmunoprecipitation experiments. Glutamine substitutions in two conserved glutamate residues, located within predicted transmembrane helices of Drosophila Orai and human Orai1, greatly diminish store-operated Ca2+ influx, and primary T cells ectopically expressing mutant E106Q and E190Q Orai1 proteins show reduced proliferation and cytokine secretion. Together, these data establish Orai1 as a predominant mediator of store-operated calcium entry, proliferation, and cytokine production in T cells.
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Affiliation(s)
- Yousang Gwack
- Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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609
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Chung SC, Limnander A, Kurosaki T, Weiss A, Korenbrot JI. Coupling Ca2+ store release to Icrac channel activation in B lymphocytes requires the activity of Lyn and Syk kinases. ACTA ACUST UNITED AC 2007; 177:317-28. [PMID: 17452533 PMCID: PMC2064139 DOI: 10.1083/jcb.200702050] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Activation of the B cell receptor complex in B lymphocytes causes Ca2+ release from intracellular stores, which, in turn, activates ion channels known as Icrac. We investigated the mechanisms that link Ca2+ store release to channel gating in DT40 B lymphocyte cell lines genetically manipulated to suppress the expression of several tyrosine kinases: Btk, Lyn, Syk, and the Blnk adaptor molecule. The simultaneous but not the independent suppression of Lyn and Syk expression prevents the activation of Icrac without interfering with thapsigargin-sensitive Ca2+ store release. Icrac activation by Ca2+ is reversed in mutant cells by the homologous expression of the missing kinases. Pharmacological inhibition of kinase activity by LavendustinA and PP2 cause the same functional deficit as the genetic suppression of enzyme expression. Biochemical assays demonstrate that kinase activity is required as a tonic signal: targets must be phosphorylated to link Ca2+ store release to Icrac gating. The action of kinases on Icrac activation does not arise from control of the expression level of the stromal interaction molecule 1 and Orai1 proteins.
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Affiliation(s)
- S Clare Chung
- Department of Physiology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
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610
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Worley PF, Zeng W, Huang GN, Yuan JP, Kim JY, Lee MG, Muallem S. TRPC channels as STIM1-regulated store-operated channels. Cell Calcium 2007; 42:205-11. [PMID: 17517433 PMCID: PMC2764400 DOI: 10.1016/j.ceca.2007.03.004] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Accepted: 03/22/2007] [Indexed: 01/18/2023]
Abstract
Receptor-activated Ca(2+) influx is mediated largely by store-operated channels (SOCs). TRPC channels mediate a significant portion of the receptor-activated Ca(2+) influx. However, whether any of the TRPC channels function as a SOC remains controversial. Our understanding of the regulation of TRPC channels and their function as SOCs is being reshaped with the discovery of the role of STIM1 in the regulation of Ca(2+) influx channels. The findings that STIM1 is an ER resident Ca(2+) binding protein that regulates SOCs allow an expanded and molecular definition of SOCs. SOCs can be considered as channels that are regulated by STIM1 and require the clustering of STIM1 in response to depletion of the ER Ca(2+) stores and its translocation towards the plasma membrane. TRPC1 and other TRPC channels fulfill these criteria. STIM1 binds to TRPC1, TRPC2, TRPC4 and TRPC5 but not to TRPC3, TRPC6 and TRPC7, and STIM1 regulates TRPC1 channel activity. Structure-function analysis reveals that the C-terminus of STIM1 contains the binding and gating function of STIM1. The ERM domain of STIM1 binds to TRPC channels and a lysine-rich region participates in the gating of SOCs and TRPC1. Knock-down of STIM1 by siRNA and prevention of its translocation to the plasma membrane inhibit the activity of native SOCs and TRPC1. These findings support the conclusion that TRPC1 is a SOC. Similar studies with other TRPC channels demonstrate their regulation by STIM1 and indicate that all TRPC channels, except TRPC7, function as SOCs.
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Affiliation(s)
- Paul F. Worley
- The department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
- The department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
- Correspondence: S. M. (); P. F. W. ()
| | - Weizhong Zeng
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology and Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752
| | - Guo N. Huang
- The department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Joseph P. Yuan
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Joo Young Kim
- Department of Pharmacology and Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752
| | - Min Goo Lee
- Department of Pharmacology and Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752
| | - Shmuel Muallem
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Correspondence: S. M. (); P. F. W. ()
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611
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Liou J, Fivaz M, Inoue T, Meyer T. Live-cell imaging reveals sequential oligomerization and local plasma membrane targeting of stromal interaction molecule 1 after Ca2+ store depletion. Proc Natl Acad Sci U S A 2007; 104:9301-6. [PMID: 17517596 PMCID: PMC1890489 DOI: 10.1073/pnas.0702866104] [Citation(s) in RCA: 503] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Stromal interaction molecule 1 (STIM1) has recently been identified by our group and others as an endoplasmic reticulum (ER) Ca(2+) sensor that responds to ER Ca(2+) store depletion and activates Ca(2+) channels in the plasma membrane (PM). The molecular mechanism by which STIM1 transduces signals from the ER lumen to the PM is not yet understood. Here we developed a live-cell FRET approach and show that STIM1 forms oligomers within 5 s after Ca(2+) store depletion. These oligomers rapidly dissociated when ER Ca(2+) stores were refilled. We further show that STIM1 formed oligomers before its translocation within the ER network to ER-PM junctions. A mutant STIM1 lacking the C-terminal polybasic PM-targeting motif oligomerized after Ca(2+) store depletion but failed to form puncta at ER-PM junctions. Using fluorescence recovery after photobleaching measurements to monitor STIM1 mobility, we show that STIM1 oligomers translocate on average only 2 mum to reach ER-PM junctions, arguing that STIM1 ER-to-PM signaling is a local process that is suitable for generating cytosolic Ca(2+) gradients. Together, our live-cell measurements dissect the STIM1 ER-to-PM signaling relay into four sequential steps: (i) dissociation of Ca(2+), (ii) rapid oligomerization, (iii) spatially restricted translocation to nearby ER-PM junctions, and (iv) activation of PM Ca(2+) channels.
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Affiliation(s)
- Jen Liou
- Department of Chemical and Systems Biology, Stanford University Medical School, 318 Campus Drive, Clark Center, Stanford, CA 94305
- *To whom correspondence may be addressed: E-mail: or
| | - Marc Fivaz
- Department of Chemical and Systems Biology, Stanford University Medical School, 318 Campus Drive, Clark Center, Stanford, CA 94305
| | - Takanari Inoue
- Department of Chemical and Systems Biology, Stanford University Medical School, 318 Campus Drive, Clark Center, Stanford, CA 94305
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford University Medical School, 318 Campus Drive, Clark Center, Stanford, CA 94305
- *To whom correspondence may be addressed: E-mail: or
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612
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Wu MM, Luik RM, Lewis RS. Some assembly required: constructing the elementary units of store-operated Ca2+ entry. Cell Calcium 2007; 42:163-72. [PMID: 17499354 PMCID: PMC2323433 DOI: 10.1016/j.ceca.2007.03.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 03/15/2007] [Accepted: 03/16/2007] [Indexed: 11/23/2022]
Abstract
The means by which Ca(2+) store depletion evokes the opening of store-operated Ca(2+) channels (SOCs) in the plasma membrane of excitable and non-excitable cells has been a longstanding mystery. Indirect evidence has supported local interactions between the ER and SOCs as well as long-range interactions mediated through a diffusible activator. The recent molecular identification of the ER Ca(2+) sensor (STIM1) and a subunit of the CRAC channel (Orai1), a prototypic SOC, has now made it possible to visualize directly the sequence of events that links store depletion to CRAC channel opening. Following store depletion, STIM1 moves from locations throughout the ER to accumulate in ER subregions positioned within 10-25nm of the plasma membrane. Simultaneously, Orai1 gathers at discrete sites in the plasma membrane directly opposite STIM1, resulting in local CRAC channel activation. These new studies define the elementary units of store-operated Ca(2+) entry, and reveal an unprecedented mechanism for channel activation in which the stimulus brings a channel and its activator/sensor together for interaction across apposed membrane compartments. We discuss the implications of this choreographic mechanism with regard to Ca(2+) dynamics, specificity of Ca(2+) signaling, and the existence of a specialized ER subset dedicated to the control of the CRAC channel.
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Affiliation(s)
- Minnie M Wu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, United States
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613
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Cahalan MD, Zhang SL, Yeromin AV, Ohlsen K, Roos J, Stauderman KA. Molecular basis of the CRAC channel. Cell Calcium 2007; 42:133-44. [PMID: 17482674 PMCID: PMC2735391 DOI: 10.1016/j.ceca.2007.03.002] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 03/13/2007] [Accepted: 03/14/2007] [Indexed: 01/28/2023]
Abstract
Ca(2+) release-activated Ca(2+) (CRAC) channels, located in the plasma membrane, are opened upon release of Ca(2+) from intracellular stores, permitting Ca(2+) entry and sustained [Ca(2+)](i) signaling that replenishes the store in numerous cell types. This mechanism is particularly important in T lymphocytes of the immune system, providing the missing link in the signal transduction cascade that is initiated by T cell receptor engagement and leads to altered expression of genes that results ultimately in the production of cytokines and cell proliferation. In the past three years, RNA interference screens together with over-expression and site-directed mutagenesis have identified the triggering molecule (Stim) that links store depletion to CRAC channel-mediated Ca(2+) influx and the pore subunit (Orai) of the CRAC channel that allows highly selective entry of Ca(2+) ions into cells.
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Affiliation(s)
- Michael D Cahalan
- Department of Physiology and Biophysics and Center for Immunology, University of California, Irvine, CA 92697, United States.
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614
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Yuan JP, Zeng W, Huang GN, Worley PF, Muallem S. STIM1 heteromultimerizes TRPC channels to determine their function as store-operated channels. Nat Cell Biol 2007; 9:636-45. [PMID: 17486119 PMCID: PMC2699187 DOI: 10.1038/ncb1590] [Citation(s) in RCA: 394] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Accepted: 04/17/2007] [Indexed: 12/22/2022]
Abstract
Stromal interacting molecule 1 (STIM1) is a Ca(2+) sensor that conveys the Ca(2+) load of the endoplasmic reticulum to store-operated channels (SOCs) at the plasma membrane. Here, we report that STIM1 binds TRPC1, TRPC4 and TRPC5 and determines their function as SOCs. Inhibition of STIM1 function inhibits activation of TRPC5 by receptor stimulation, but not by La(3+), suggesting that STIM1 is obligatory for activation of TRPC channels by agonists, but STIM1 is not essential for channel function. Through a distinct mechanism, STIM1 also regulates TRPC3 and TRPC6. STIM1 does not bind TRPC3 and TRPC6, and regulates their function indirectly by mediating the heteromultimerization of TRPC3 with TRPC1 and TRPC6 with TRPC4. TRPC7 is not regulated by STIM1. We propose a new definition of SOCs, as channels that are regulated by STIM1 and require the store depletion-mediated clustering of STIM1. By this definition, all TRPC channels, except TRPC7, function as SOCs.
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Affiliation(s)
- Joseph P. Yuan
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Weizhong Zeng
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Guo N. Huang
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Paul F. Worley
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Correspondence should be addressed to S.M. or P.F.W. (e-mail: ; pworley.edu; )
| | - Shmuel Muallem
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Correspondence should be addressed to S.M. or P.F.W. (e-mail: ; pworley.edu; )
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615
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Abstract
Capacitative Ca2+ entry links the emptying of intracellular Ca2+ stores to the activation of store-operated Ca2+ channels in the plasma membrane. In the twenty years since the inception of the concept of capacitative Ca2+ entry, a number of activation mechanisms have been proposed, and there has been considerable interest in the possibility that TRP channels function as store-operated channels. However, in the past two years, two major players in both the signaling and permeation mechanisms for store-operated channels have been discovered: Stim1 and the Orai proteins. Stim1 is an endoplasmic reticulum Ca2+ sensor. It appears to act by redistributing within a small component of the endoplasmic reticulum, approaching the plasma membrane, but does not seem to translocate into the plasma membrane. Stim1 signals to plasma membrane Orai proteins, which constitute pore-forming subunits of store-operated channels.
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Affiliation(s)
- James W Putney
- National Institute of Environmental Health Sciences - NIH, PO Box 12233, Research Triangle Park, NC 27709, USA.
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616
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Dissecting ICRAC, a store-operated calcium current. Trends Biochem Sci 2007; 32:235-45. [PMID: 17434311 DOI: 10.1016/j.tibs.2007.03.009] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Revised: 03/05/2007] [Accepted: 03/28/2007] [Indexed: 02/02/2023]
Abstract
The use of Ca(2+) for intracellular signalling necessitates tight local and global control of cytoplasmic Ca(2+) concentration, and mechanisms for maintaining the net Ca(2+) balance. It has long been recognized that intracellular Ca(2+) stores exert control over Ca(2+) influx at the plasma membrane through a process of store-operated Ca(2+) entry (SOCE). The Ca(2+) current I(CRAC) is the best characterized instance of SOCE, but the elements of the pathway leading to I(CRAC) have eluded biochemical definition for more than a decade. However, the recent identification of key proteins underlying I(CRAC)--STIM1 and Orai1--has led to several insights into this ER-to-plasma membrane signalling system and to the recognition that it is an ancient and conserved mechanism in multicellular organisms.
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617
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Abstract
Store-operated calcium channels (SOCs) serve essential functions from secretion and motility to gene expression and cell growth. A fundamental mystery is how the depletion of Ca2+ from the endoplasmic reticulum (ER) activates Ca2+ entry through SOCs in the plasma membrane. Recent studies using genetic approaches have identified genes encoding the ER Ca2+ sensor and a prototypic SOC, the Ca2+-release-activated Ca2+ (CRAC) channel. New findings reveal a unique mechanism for channel activation, in which the CRAC channel and its sensor migrate independently to closely apposed sites of interaction in the ER and the plasma membrane.
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Affiliation(s)
- Richard S Lewis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA.
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618
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Jousset H, Frieden M, Demaurex N. STIM1 Knockdown Reveals That Store-operated Ca2+ Channels Located Close to Sarco/Endoplasmic Ca2+ ATPases (SERCA) Pumps Silently Refill the Endoplasmic Reticulum. J Biol Chem 2007; 282:11456-64. [PMID: 17283081 DOI: 10.1074/jbc.m609551200] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stromal interaction molecule (STIM) proteins are putative ER Ca2+ sensors that recruit and activate store-operated Ca2+ (SOC) channels at the plasma membrane, a process triggered by the Ca2+ depletion of the endoplasmic reticulum (ER). To test whether STIM1 is required for ER refilling, we used RNA interference and measured Ca2+ signals in the cytosol, the ER, and the mitochondria of HeLa cells. Knockdown of STIM1 (mRNA levels, 73%) reduced SOC entry by 73% when sarco/endoplasmic Ca2+ ATPases (SERCA) were inhibited by thapsigargin but did not prevent Ca2+ stores refilling when cells were stimulated by physiological agonists. Stores could be fully refilled by increasing the external Ca2+ concentration above physiological values, but no cytosolic Ca2+ signals were detected during store refilling even at very high Ca2+ concentrations. [Ca2+](ER) measurements revealed that the basal activity of SERCA was not affected in STIM1 knockdown cells and that [Ca2+](ER) levels were restored within 2 min in physiological saline following store depletion. Mitochondrial inhibitors reduced ER refilling in wild-type but not in STIM1 knockdown cells, indicating that ER refilling does not require functional mitochondria at low STIM1 levels. Our data show that ER refilling is largely preserved at reduced STIM1 levels, despite a drastic reduction of store-operated Ca2+ entry, because Ca2+ ions are directly transferred from SOC channels to SERCA. These findings are consistent with the formation of microdomains containing not only SOC channels on the plasma membrane and STIM proteins on the ER but also SERCA pumps and mitochondria to refill the ER without perturbing the cytosol.
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Affiliation(s)
- Hélène Jousset
- Department of Cell Physiology and Metabolism, University of Geneva Medical School, 1 Michel-Servet, CH-1211 Geneva 4, Switzerland
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619
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Shuttleworth TJ, Thompson JL, Mignen O. STIM1 and the noncapacitative ARC channels. Cell Calcium 2007; 42:183-91. [PMID: 17391754 PMCID: PMC1995027 DOI: 10.1016/j.ceca.2007.01.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Revised: 01/25/2007] [Accepted: 01/26/2007] [Indexed: 10/23/2022]
Abstract
Our understanding of the nature and regulation of receptor-activated Ca(2+) entry in nonexcitable cells has recently undergone a radical change that began with the identification of the stromal interacting molecule proteins (e.g., STIM1) as playing a critical role in the regulation of the capacitative, or store-operated, Ca(2+) entry. As such, current models emphasize the role of STIM1 located in the endoplasmic reticulum membrane, where it senses the status of the intracellular Ca(2+) stores via a luminal N-terminal Ca(2+)-binding EF-hand domain. Dissociation of Ca(2+) from this domain induces the clustering of STIM1 to regions of the ER that lie close to the plasma membrane, where it regulates the activity of the store-operated Ca(2+) channels (e.g., CRAC channels). Thus, the specific dependence on store-depletion, and the role of the Ca(2+)-binding EF-hand domain in this process, are critical to all current models of the action of STIM1 on Ca(2+) entry. However, until recently, the effects of STIM1 on other modes of receptor-activated Ca(2+) entry have not been examined. Surprisingly, we found that STIM1 exerts similar, although not identical, actions on the arachidonic acid-regulated Ca(2+)-selective (ARC) channels-a widely expressed mode of agonist-activated Ca(2+) entry whose activation is completely independent of Ca(2+) store depletion. Regulation of the ARC channels by STIM1 is not only independent of store depletion, but also of the Ca(2+)-binding function of the EF-hand, and translocation of STIM1 to the plasma membrane. Instead, it is the pool of STIM1 that constitutively resides in the plasma membrane that is critical for the regulation of the ARC channels. Thus, ARC channel activity is selectively inhibited by exposure of intact cells to an antibody targeting the extracellular N-terminal domain of STIM1. Similarly, introducing mutations in STIM1 that prevent the N-linked glycosylation-dependent constitutive expression of the protein in the plasma membrane specifically inhibits the activity of the ARC channels without affecting the CRAC channels. These studies demonstrate that STIM1 is a far more universal regulator of Ca(2+) entry pathways than previously assumed, and has multiple, and entirely distinct, modes of action. Precisely how this same protein can act in such separate and specific ways on these different pathways of agonist-activated Ca(2+)entry remains an intriguing, yet currently unresolved, question.
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Affiliation(s)
- Trevor J Shuttleworth
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA.
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620
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Strange K, Yan X, Lorin-Nebel C, Xing J. Physiological roles of STIM1 and Orai1 homologs and CRAC channels in the genetic model organism Caenorhabditis elegans. Cell Calcium 2007; 42:193-203. [PMID: 17376526 PMCID: PMC2066184 DOI: 10.1016/j.ceca.2007.02.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 02/09/2007] [Accepted: 02/12/2007] [Indexed: 12/18/2022]
Abstract
The nematode Caenorhabditis elegans provides numerous experimental advantages for developing an integrative molecular understanding of physiological processes and has proven to be a valuable model for characterizing Ca(2+) signaling mechanisms. This review will focus on the role of Ca(2+) release activated Ca(2+) (CRAC) channel activity in function of the worm gonad and intestine. Inositol 1,4,5-trisphosphate (IP(3))-dependent oscillatory Ca(2+) signaling regulates contractile activity of the gonad and rhythmic posterior body wall muscle contraction (pBoc) required for ovulation and defecation, respectively. The C. elegans genome contains a single homolog of both STIM1 and Orai1, proteins required for CRAC channel function in mammalian and Drosophila cells. C. elegans STIM-1 and ORAI-1 are coexpressed in the worm gonad and intestine and give rise to robust CRAC channel activity when coexpressed in HEK293 cells. STIM-1 or ORAI-1 knockdown causes complete sterility demonstrating that the genes are essential components of gonad Ca(2+) signaling. Knockdown of either protein dramatically inhibits intestinal cell CRAC channel activity, but surprisingly has no effect on pBoc, intestinal Ca(2+) oscillations or intestinal ER Ca(2+) store homeostasis. CRAC channels thus do not play obligate roles in all IP(3)-dependent signaling processes in C. elegans. Instead, we suggest that CRAC channels carry out highly specialized and cell specific signaling roles and that they may function as a failsafe mechanism to prevent Ca(2+) store depletion under pathophysiological and stress conditions.
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Affiliation(s)
- Kevin Strange
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232-2520, United States.
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621
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Cai X. Molecular evolution and structural analysis of the Ca(2+) release-activated Ca(2+) channel subunit, Orai. J Mol Biol 2007; 368:1284-91. [PMID: 17400243 DOI: 10.1016/j.jmb.2007.03.022] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 03/07/2007] [Accepted: 03/08/2007] [Indexed: 12/15/2022]
Abstract
Depletion of intracellular Ca(2+) stores evokes Ca(2+) entry across the plasma membrane by inducing Ca(2+) release-activated Ca(2+) (CRAC) currents in many cell types. Recently, Orai and STIM proteins were identified as the molecular identities of the CRAC channel subunit and the endoplasmic reticulum Ca(2+) sensor, respectively. Here, extensive database searching and phylogenetic analysis revealed several lineage-specific duplication events in the Orai protein family, which may account for the evolutionary origins of distinct functional properties among mammalian Orai proteins. Based on similarity to key structural domains and essential residues for channel functions in Orai proteins, database searching also identifies a putative primordial Orai sequence in hyperthermophilic archaeons. Furthermore, modern Orai appears to acquire new structural domains as early as Urochodata, before divergence into vertebrates. The evolutionary patterns of structural domains might be related to distinct functional properties of Drosophila and mammalian CRAC currents. Interestingly, Orai proteins display two conserved internal repeats located at transmembrane segments 1 and 3, both of which contain key amino acids essential for channel function. These findings demonstrate biochemical and physiological relevance of Orai proteins in light of different evolutionary origins and will provide novel insights into future structural and functional studies of Orai proteins.
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Affiliation(s)
- Xinjiang Cai
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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622
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Liao Y, Erxleben C, Yildirim E, Abramowitz J, Armstrong DL, Birnbaumer L. Orai proteins interact with TRPC channels and confer responsiveness to store depletion. Proc Natl Acad Sci U S A 2007; 104:4682-7. [PMID: 17360584 PMCID: PMC1838661 DOI: 10.1073/pnas.0611692104] [Citation(s) in RCA: 253] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The TRPC (C-type transient receptor potential) class of ion channels has been hypothesized to participate in store-operated Ca(2+) entry (SOCE). Recently, however, STIM1 and Orai1 proteins have been proposed to form SOCE channels. Whether TRPCs participate in SOCE that is dependent on or regulated by Orai has not been explored. Here we show that Orai1 physically interacts with the N and C termini of TRPC3 and TRPC6, and that in cells overexpressing either TRPC3 or TRPC6 in a store-depletion insensitive manner, these TRPCs become sensitive to store depletion upon expression of an exogenous Orai. Thus, Orai-1, -2, and -3 enhanced thapsigargin-induced calcium entry by 50-150% in cells stably overexpressing either TRPC3 or TRPC6. Orai1 expression had no significant effect on endogenous, thapsigargin-induced calcium entry in wild-type cells (HEK-293, COS1), in HEK cells expressing a thapsigargin-sensitive variant of TRPC3 (TRPC3a), or in HEK cells overexpressing another membrane protein, V1aR. Single-channel cation currents present in membrane patches of TRPC3-overexpressing cells were suppressed by expression of Orai1. We propose that Orai proteins by interacting with TRPCs act as regulatory subunits that confer STIM1-mediated store depletion sensitivity to these channels.
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Affiliation(s)
| | - Christian Erxleben
- Neurobiology Laboratories, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709
| | | | | | - David L. Armstrong
- Neurobiology Laboratories, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709
- To whom correspondence may be addressed. E-mail: or
| | - Lutz Birnbaumer
- *Signal Transduction and
- To whom correspondence may be addressed. E-mail: or
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623
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Hauser CT, Tsien RY. A hexahistidine-Zn2+-dye label reveals STIM1 surface exposure. Proc Natl Acad Sci U S A 2007; 104:3693-7. [PMID: 17360414 PMCID: PMC1805700 DOI: 10.1073/pnas.0611713104] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Indexed: 01/31/2023] Open
Abstract
Site-specific fluorescent labeling of proteins in vivo remains one of the most powerful techniques for imaging complex processes in live cells. Although fluorescent proteins in many colors are useful tools for tracking expression and localization of fusion proteins in cells, these relatively large tags (>220 aa) can perturb protein folding, trafficking and function. Much smaller genetically encodable domains (<15 aa) offer complementary advantages. We introduce a small fluorescent chelator whose membrane-impermeant complex with nontoxic Zn(2+) ions binds tightly but reversibly to hexahistidine (His(6)) motifs on surface-exposed proteins. This live-cell label helps to resolve a current controversy concerning externalization of the stromal interaction molecule STIM1 upon depletion of Ca(2+) from the endoplasmic reticulum. Whereas N-terminal fluorescent protein fusions interfere with surface exposure of STIM1, short His(6) tags are accessible to the dye or antibodies, demonstrating externalization.
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Affiliation(s)
| | - Roger Y. Tsien
- Departments of *Pharmacology and
- Chemistry and Biochemistry, and
- Howard Hughes Medical Institute, University of California at San Diego, La Jolla, CA 92093-0647
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624
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Takahashi Y, Murakami M, Watanabe H, Hasegawa H, Ohba T, Munehisa Y, Nobori K, Ono K, Iijima T, Ito H. Essential role of the N-terminus of murine Orai1 in store-operated Ca2+ entry. Biochem Biophys Res Commun 2007; 356:45-52. [PMID: 17343823 DOI: 10.1016/j.bbrc.2007.02.107] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 02/14/2007] [Indexed: 10/23/2022]
Abstract
Store-operated Ca(2+) entry (SOCE) is a physiologically important process that is triggered by intracellular Ca(2+) depletion. Recently, human Orai1 (the channel-forming subunit) and STIM1 (the calcium sensor) were identified as essential molecules for SOCE. Here, we report the cloning and functional analysis of three murine orthologs of Orai1, termed Orai1, 2, and 3. Among the genes identified, Orai1 contains a distinctive proline- and arginine-rich N-terminal cytoplasmic sequence. Co-expression of STIM1 with Orai1 produced a marked effect on SOCE, while co-expression with Orai2 or Orai3 had little effect. Expression of Orai1 without its N-terminal tail had a marginal effect on SOCE, while chimeric Orai2 containing the Orai1 N-terminus produced a marked increase in SOCE. In addition, a truncated version of Orai1 containing the N-terminus without the pore-forming transmembrane domain had a dominant negative effect on SOCE. These results reveal the essential role of Orai1 and its N-terminal sequence in SOCE.
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Affiliation(s)
- Yoichiro Takahashi
- Second Department of Internal Medicine, Akita University School of Medicine, Akita, Japan
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625
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Ong HL, Liu X, Tsaneva-Atanasova K, Singh BB, Bandyopadhyay BC, Swaim WD, Russell JT, Hegde RS, Sherman A, Ambudkar IS. Relocalization of STIM1 for activation of store-operated Ca(2+) entry is determined by the depletion of subplasma membrane endoplasmic reticulum Ca(2+) store. J Biol Chem 2007; 282:12176-85. [PMID: 17298947 PMCID: PMC3309416 DOI: 10.1074/jbc.m609435200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
STIM1 (stromal interacting molecule 1), an endoplasmic reticulum (ER) protein that controls store-operated Ca(2+) entry (SOCE), redistributes into punctae at the cell periphery after store depletion. This redistribution is suggested to have a causal role in activation of SOCE. However, whether peripheral STIM1 punctae that are involved in regulation of SOCE are determined by depletion of peripheral or more internal ER has not yet been demonstrated. Here we show that Ca(2+) depletion in subplasma membrane ER is sufficient for peripheral redistribution of STIM1 and activation of SOCE. 1 microM thapsigargin (Tg) induced substantial depletion of intracellular Ca(2+) stores and rapidly activated SOCE. In comparison, 1 nM Tg induced slower, about 60-70% less Ca(2+) depletion but similar SOCE. SOCE was confirmed by measuring I(SOC) in addition to Ca(2+), Mn(2+), and Ba(2+) entry. Importantly, 1 nM Tg caused redistribution of STIM1 only in the ER-plasma membrane junction, whereas 1 microM Tg caused a relatively global relocalization of STIM1 in the cell. During the time taken for STIM1 relocalization and SOCE activation, 1 nM Bodipy-fluorescein Tg primarily labeled the subplasma membrane region, whereas 1 microM Tg labeled the entire cell. The localization of Tg in the subplasma membrane region was associated with depletion of ER in this region and activation of SOCE. Together, these data suggest that peripheral STIM1 relocalization that is causal in regulation of SOCE is determined by the status of [Ca(2+)] in the ER in close proximity to the plasma membrane. Thus, the mechanism involved in regulation of SOCE is contained within the ER-plasma membrane junctional region.
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Affiliation(s)
- Hwei Ling Ong
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Xibao Liu
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | | | - Brij B. Singh
- Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58203
| | - Bidhan C. Bandyopadhyay
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - William D. Swaim
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - James T. Russell
- Microscopy and Imaging Core, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Ramanujan S. Hegde
- Cell Biology and Metabolism Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Arthur Sherman
- Laboratory of Biological Modeling, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Indu S. Ambudkar
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
- To whom correspondence should be addressed: Bldg. 10, Rm. 1N-113, 10 Center Dr., National Institutes of Health, Bethesda, MD 20892. Tel.: 301-496-5298; Fax: 301-402-1228;
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626
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Amaral MD, Chapleau CA, Pozzo-Miller L. Transient receptor potential channels as novel effectors of brain-derived neurotrophic factor signaling: potential implications for Rett syndrome. Pharmacol Ther 2007; 113:394-409. [PMID: 17118456 PMCID: PMC1862519 DOI: 10.1016/j.pharmthera.2006.09.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Accepted: 09/26/2006] [Indexed: 02/07/2023]
Abstract
In addition to their prominent role as survival signals for neurons in the developing nervous system, neurotrophins have established their significance in the adult brain as well, where their modulation of synaptic transmission and plasticity may participate in associative learning and memory. These crucial activities are primarily the result of neurotrophin regulation of intracellular Ca(2+) homeostasis and, ultimately, changes in gene expression. Outlined in the following review is a synopsis of neurotrophin signaling with a particular focus upon brain-derived neurotrophic factor (BDNF) and its role in hippocampal synaptic plasticity and neuronal Ca(2+) homeostasis. Neurotrophin signaling through tropomyosin-related kinase (Trk) and pan-neurotrophin receptor 75 kD (p75(NTR)) receptors are also discussed, reviewing recent results that indicate signaling through these two receptor modalities leads to opposing cellular outcomes. We also provide an intriguing look into the transient receptor potential channel (TRPC) family of ion channels as distinctive targets of BDNF signaling; these channels are critical for capacitative Ca(2+) entry, which, in due course, mediates changes in neuronal structure including dendritic spine density. Finally, we expand these topics into an exploration of mental retardation (MR), in particular Rett Syndrome (RTT), where dendritic spine abnormalities may underlie cognitive impairments. We propose that understanding the role of neurotrophins in synapse formation, plasticity, and maintenance will make fundamental contributions to the development of therapeutic strategies to improve cognitive function in developmental disorders associated with MR.
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Affiliation(s)
- Michelle D Amaral
- Department of Neurobiology, Civitan International Research Center, McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294-2182, USA
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627
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Luik RM, Lewis RS. New insights into the molecular mechanisms of store-operated Ca2+ signaling in T cells. Trends Mol Med 2007; 13:103-7. [PMID: 17267286 DOI: 10.1016/j.molmed.2007.01.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 12/14/2006] [Accepted: 01/19/2007] [Indexed: 12/28/2022]
Abstract
The activation of Ca(2+) entry through store-operated channels by agonists that deplete Ca(2+) from the endoplasmic reticulum (ER) is an ubiquitous signaling mechanism, the molecular basis of which has remained elusive for the past 20 years. In T lymphocytes, store-operated Ca(2+)-release-activated Ca(2+) (CRAC) channels constitute the sole pathway for Ca(2+) entry following antigen-receptor engagement, and their function is essential for driving the program of gene expression that underlies T-cell activation by antigen. The first molecular components of this pathway have recently been identified: stromal interaction molecule 1 (STIM1), the ER Ca(2+) sensor, and Orai1, a pore-forming subunit of the CRAC channel. Recent work shows that CRAC channels are activated in a complex fashion that involves the co-clustering of STIM1 in junctional ER directly opposite Orai1 in the plasma membrane. These studies reveal an abundance of sites where Ca(2+) signaling might be controlled to modulate the activity of T cells during the immune response.
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Affiliation(s)
- Riina M Luik
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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628
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Ong HL, Cheng KT, Liu X, Bandyopadhyay BC, Paria BC, Soboloff J, Pani B, Gwack Y, Srikanth S, Singh BB, Gill D, Ambudkar IS. Dynamic assembly of TRPC1-STIM1-Orai1 ternary complex is involved in store-operated calcium influx. Evidence for similarities in store-operated and calcium release-activated calcium channel components. J Biol Chem 2007; 282:9105-16. [PMID: 17224452 PMCID: PMC3309402 DOI: 10.1074/jbc.m608942200] [Citation(s) in RCA: 311] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Store-operated calcium entry (SOCE) is a ubiquitous mechanism that is mediated by distinct SOC channels, ranging from the highly selective calcium release-activated Ca2+ (CRAC) channel in rat basophilic leukemia and other hematopoietic cells to relatively Ca2+-selective or non-selective SOC channels in other cells. Although the exact composition of these channels is not yet established, TRPC1 contributes to SOC channels and regulation of physiological function of a variety of cell types. Recently, Orai1 and STIM1 have been suggested to be sufficient for generating CRAC channels. Here we show that Orai1 and STIM1 are also required for TRPC1-SOC channels. Knockdown of TRPC1, Orai1, or STIM1 attenuated, whereas overexpression of TRPC1, but not Orai1 or STIM1, induced an increase in SOC entry and I(SOC) in human salivary gland cells. All three proteins were co-localized in the plasma membrane region of cells, and thapsigargin increased co-immunoprecipitation of TRPC1 with STIM1, and Orai1 in human salivary gland cells as well as dispersed mouse submandibular gland cells. In aggregate, the data presented here reveal that all three proteins are essential for generation of I(SOC) in these cells and that dynamic assembly of TRPC1-STIM1-Orai1 ternary complex is involved in activation of SOC channel in response to internal Ca2+ store depletion. Thus, these data suggest a common molecular basis for SOC and CRAC channels.
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Affiliation(s)
- Hwei Ling Ong
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Kwong Tai Cheng
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Xibao Liu
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Bidhan C. Bandyopadhyay
- Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58203
| | - Biman C. Paria
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Jonathan Soboloff
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Biswaranjan Pani
- Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58203
| | - Yousang Gwack
- Department of Pathology, Harvard Medical School and the CBR Institute of Biomedical Research, Boston, Massachusetts 02115
| | - Sonal Srikanth
- Department of Pathology, Harvard Medical School and the CBR Institute of Biomedical Research, Boston, Massachusetts 02115
| | - Brij B. Singh
- Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58203
| | - Donald Gill
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Indu S. Ambudkar
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
- To whom correspondence should be addressed: Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, NIH, Bldg. 10, Rm. 1N-113,10 Center Drive, Bethesda,MD20892. Tel.: 301-496-5298; Fax: 301-402-1228;
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629
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Lorin-Nebel C, Xing J, Yan X, Strange K. CRAC channel activity in C. elegans is mediated by Orai1 and STIM1 homologues and is essential for ovulation and fertility. J Physiol 2007; 580:67-85. [PMID: 17218360 PMCID: PMC2075418 DOI: 10.1113/jphysiol.2006.124883] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The Ca(2+) release-activated Ca(2+) (CRAC) channel is a plasma membrane Ca(2+) entry pathway activated by endoplasmic reticulum (ER) Ca(2+) store depletion. STIM1 proteins function as ER Ca(2+) sensors and regulate CRAC channel activation. Recent studies have demonstrated that CRAC channels are encoded by the human Orai1 gene and a homologous Drosophila gene. C. elegans intestinal cells express a store-operated Ca(2+) channel (SOCC) regulated by STIM-1. We cloned a full-length C. elegans cDNA that encodes a 293 amino acid protein, ORAI-1, homologous to human and Drosophila Orai1 proteins. ORAI-1 GFP reporters are co-expressed with STIM-1 in the gonad and intestine. Inositol 1,4,5-trisphosphate (IP(3))-dependent Ca(2+) signalling regulates C. elegans gonad function, fertility and rhythmic posterior body wall muscle contraction (pBoc) required for defecation. RNA interference (RNAi) silencing of orai-1 expression phenocopies stim-1 knockdown and causes sterility and prevents intestinal cell SOCC activation, but has no effect on pBoc or intestinal Ca(2+) signalling. Orai-1 RNAi suppresses pBoc defects induced by intestinal expression of a STIM-1 Ca(2+)-binding mutant, indicating that the proteins function in a common pathway. Co-expression of stim-1 and orai-1 cDNAs in HEK293 cells induces large inwardly rectifying cation currents activated by ER Ca(2+) depletion. The properties of this current recapitulate those of the native SOCC current. We conclude that C. elegans expresses bona fide CRAC channels that require the function of Orai1- and STIM1-related proteins. CRAC channels thus arose very early in animal evolution. In C. elegans, CRAC channels do not play obligate roles in all IP(3)-dependent signalling processes and ER Ca(2+) homeostasis. Instead, we suggest that CRAC channels carry out highly specialized and cell-specific signalling roles and that they may function as a failsafe mechanism to prevent Ca(2+) store depletion under pathophysiological and stress conditions.
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Affiliation(s)
- Catherine Lorin-Nebel
- Vanderbilt University Medical Center, T-4208 Medical Center North, Nashville, TN 37232-2520, USA
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630
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Mignen O, Thompson JL, Shuttleworth TJ. STIM1 regulates Ca2+ entry via arachidonate-regulated Ca2+-selective (ARC) channels without store depletion or translocation to the plasma membrane. J Physiol 2006; 579:703-15. [PMID: 17158173 PMCID: PMC2151373 DOI: 10.1113/jphysiol.2006.122432] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Recent studies have indicated a critical role for STIM (stromal interacting molecule) proteins in the regulation of the store-operated mode of receptor-activated Ca2+ entry. Current models emphasize the role of STIM located in the endoplasmic reticulum membrane, where a Ca2+-binding EF-hand domain within the N-terminal of the protein lies within the lumen and is thought to represent the sensor for the depletion of intracellular Ca2+ stores. Dissociation of Ca2+ from this domain induces the aggregation of STIM to regions of the ER immediately adjacent to the plasma membrane where it acts to regulate the activity of store-operated Ca2+ channels. However, the possible effects of STIM on other modes of receptor-activated Ca2+ entry have not been examined. Here we show that STIM1 also regulates the arachidonic-acid-regulated Ca2+-selective (ARC) channels - receptor-activated Ca2+ entry channels whose activation is entirely independent of store depletion. Regulation of the ARC channels by STIM1 does not involve dissociation of Ca2+ from the EF-hand, or any translocation of STIM1. Instead, a critical role of STIM1 resident in the plasma membrane is indicated. Thus, exposure of intact cells to an antibody targeting the extracellular N-terminal domain of STIM1 inhibits ARC channel activity without significantly affecting the store-operated channels. A similar specific inhibition of the ARC channels is seen in cells expressing a STIM1 construct in which the N-linked glycosylation sites essential for the constitutive cell surface expression of STIM1, were mutated. We conclude that, in contrast to store-operated channels, regulation of ARC channels by STIM1 depends exclusively on the pool of STIM1 constitutively residing in the plasma membrane. These data demonstrate that STIM1 is a more universal regulator of Ca2+ entry pathways than previously thought, and appears to have multiple modes of action.
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Affiliation(s)
- Olivier Mignen
- Department of Pharmacology and Physiology, Box 711, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA
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631
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You lose some, you gain some. Nat Rev Mol Cell Biol 2006. [DOI: 10.1038/nrm2044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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632
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Luik RM, Wu MM, Buchanan J, Lewis RS. The elementary unit of store-operated Ca2+ entry: local activation of CRAC channels by STIM1 at ER-plasma membrane junctions. ACTA ACUST UNITED AC 2006; 174:815-25. [PMID: 16966423 PMCID: PMC2064336 DOI: 10.1083/jcb.200604015] [Citation(s) in RCA: 511] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The activation of store-operated Ca2+ entry by Ca2+ store depletion has long been hypothesized to occur via local interactions of the endoplasmic reticulum (ER) and plasma membrane, but the structure involved has never been identified. Store depletion causes the ER Ca2+ sensor stromal interacting molecule 1 (STIM1) to form puncta by accumulating in junctional ER located 10–25 nm from the plasma membrane (see Wu et al. on p. 803 of this issue). We have combined total internal reflection fluorescence (TIRF) microscopy and patch-clamp recording to localize STIM1 and sites of Ca2+ influx through open Ca2+ release–activated Ca2+ (CRAC) channels in Jurkat T cells after store depletion. CRAC channels open only in the immediate vicinity of STIM1 puncta, restricting Ca2+ entry to discrete sites comprising a small fraction of the cell surface. Orai1, an essential component of the CRAC channel, colocalizes with STIM1 after store depletion, providing a physical basis for the local activation of Ca2+ influx. These studies reveal for the first time that STIM1 and Orai1 move in a coordinated fashion to form closely apposed clusters in the ER and plasma membranes, thereby creating the elementary unit of store-operated Ca2+ entry.
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Affiliation(s)
- Riina M Luik
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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633
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Xu P, Lu J, Li Z, Yu X, Chen L, Xu T. Aggregation of STIM1 underneath the plasma membrane induces clustering of Orai1. Biochem Biophys Res Commun 2006; 350:969-76. [PMID: 17045966 DOI: 10.1016/j.bbrc.2006.09.134] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2006] [Accepted: 09/26/2006] [Indexed: 11/30/2022]
Abstract
STIM1 and Orai1 have recently been identified to be crucial in the regulation of store-operated Ca(2+) entry. However, it remains to be established how STIM1 couples store depletion to the functioning of Orai1 in the plasma membrane. Using quantitative measurement, we find little STIM1 on the surface membrane which is not increased by store depletion. We further demonstrate that Orai1 assembles into clusters that co-localize with STIM1 aggregations upon store depletion. The clustering of Orai1 is only seen when Oari1 are co-expressed with STIM1, but not when expressed alone. Moreover, ER retreat from cell periphery leads to mismatching of Orai1 and STIM1 puncta. Therefore, we propose that store depletion causes aggregation and translocation of STIM1 in close apposition to the plasma membrane, which in turn recruits Orai1 in the plasma membrane to the sites of STIM1 aggregates to assemble functional units of CRAC channels in a stoichiometric manner.
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Affiliation(s)
- Pingyong Xu
- National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Science, Beijing 100101, PR China
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