Blog
About

  • Record: found
  • Abstract: found
  • Article: not found

The elementary unit of store-operated Ca2+ entry: local activation of CRAC channels by STIM1 at ER–plasma membrane junctions

Read this article at

ScienceOpenPublisherPMC
Bookmark
      There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

      Abstract

      The activation of store-operated Ca 2+ entry by Ca 2+ 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 Ca 2+ 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. [Related article:]803 of this issue). We have combined total internal reflection fluorescence (TIRF) microscopy and patch-clamp recording to localize STIM1 and sites of Ca 2+ influx through open Ca 2+ release–activated Ca 2+ (CRAC) channels in Jurkat T cells after store depletion. CRAC channels open only in the immediate vicinity of STIM1 puncta, restricting Ca 2+ 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 Ca 2+ 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 Ca 2+ entry.

      Related collections

      Most cited references 32

      • Record: found
      • Abstract: found
      • Article: not found

      Improved monomeric red, orange and yellow fluorescent proteins derived from Discosoma sp. red fluorescent protein.

      Fluorescent proteins are genetically encoded, easily imaged reporters crucial in biology and biotechnology. When a protein is tagged by fusion to a fluorescent protein, interactions between fluorescent proteins can undesirably disturb targeting or function. Unfortunately, all wild-type yellow-to-red fluorescent proteins reported so far are obligately tetrameric and often toxic or disruptive. The first true monomer was mRFP1, derived from the Discosoma sp. fluorescent protein "DsRed" by directed evolution first to increase the speed of maturation, then to break each subunit interface while restoring fluorescence, which cumulatively required 33 substitutions. Although mRFP1 has already proven widely useful, several properties could bear improvement and more colors would be welcome. We report the next generation of monomers. The latest red version matures more completely, is more tolerant of N-terminal fusions and is over tenfold more photostable than mRFP1. Three monomers with distinguishable hues from yellow-orange to red-orange have higher quantum efficiencies.
        Bookmark
        • Record: found
        • Abstract: found
        • Article: not found

        STIM is a Ca2+ sensor essential for Ca2+-store-depletion-triggered Ca2+ influx.

        Ca(2+) signaling in nonexcitable cells is typically initiated by receptor-triggered production of inositol-1,4,5-trisphosphate and the release of Ca(2+) from intracellular stores. An elusive signaling process senses the Ca(2+) store depletion and triggers the opening of plasma membrane Ca(2+) channels. The resulting sustained Ca(2+) signals are required for many physiological responses, such as T cell activation and differentiation. Here, we monitored receptor-triggered Ca(2+) signals in cells transfected with siRNAs against 2,304 human signaling proteins, and we identified two proteins required for Ca(2+)-store-depletion-mediated Ca(2+) influx, STIM1 and STIM2. These proteins have a single transmembrane region with a putative Ca(2+) binding domain in the lumen of the endoplasmic reticulum. Ca(2+) store depletion led to a rapid translocation of STIM1 into puncta that accumulated near the plasma membrane. Introducing a point mutation in the STIM1 Ca(2+) binding domain resulted in prelocalization of the protein in puncta, and this mutant failed to respond to store depletion. Our study suggests that STIM proteins function as Ca(2+) store sensors in the signaling pathway connecting Ca(2+) store depletion to Ca(2+) influx.
          Bookmark
          • Record: found
          • Abstract: found
          • Article: not found

          A mutation in Orai1 causes immune deficiency by abrogating CRAC channel function.

          Antigen stimulation of immune cells triggers Ca2+ entry through Ca2+ release-activated Ca2+ (CRAC) channels, promoting the immune response to pathogens by activating the transcription factor NFAT. We have previously shown that cells from patients with one form of hereditary severe combined immune deficiency (SCID) syndrome are defective in store-operated Ca2+ entry and CRAC channel function. Here we identify the genetic defect in these patients, using a combination of two unbiased genome-wide approaches: a modified linkage analysis with single-nucleotide polymorphism arrays, and a Drosophila RNA interference screen designed to identify regulators of store-operated Ca2+ entry and NFAT nuclear import. Both approaches converged on a novel protein that we call Orai1, which contains four putative transmembrane segments. The SCID patients are homozygous for a single missense mutation in ORAI1, and expression of wild-type Orai1 in SCID T cells restores store-operated Ca2+ influx and the CRAC current (I(CRAC)). We propose that Orai1 is an essential component or regulator of the CRAC channel complex.
            Bookmark

            Author and article information

            Affiliations
            Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305
            Author notes

            Correspondence to Richard S. Lewis: rslewis@ 123456stanford.edu

            Journal
            J Cell Biol
            JCB
            The Journal of Cell Biology
            The Rockefeller University Press
            0021-9525
            1540-8140
            11 September 2006
            : 174
            : 6
            : 815-825
            2064336
            16966423
            200604015
            10.1083/jcb.200604015
            Copyright © 2006, The Rockefeller University Press
            Product
            Categories
            Research Articles
            Article

            Cell biology

            Comments

            Comment on this article